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{\Large

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{\sc The GNU General Public License for Businesspeople and Developers } \\

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A Tutorial By:

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Bradley M. Kuhn

Executive Director

Free Software Foundation


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Copyright \copyright{} 2003 \hspace{.2in} Free Software Foundation, Inc.

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Verbatim copying and distribution of this entire document is permitted in
any medium, provided this notice is preserved.
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\begin{abstract}


This tutorial gives a section-by-section explanation of the most popular
Free Software copyright license, the GNU General Public License (GNU GPL),
and teaches software developers, managers and business people how to use
the GPL and GPL'ed software successfully in a new Free Software business and
in existing, successful enterprises.

Attendees should have a general familiarity with software development
processes.  A vague understanding of how copyright law applies to software
is also helpful.  The tutorial is of most interest to software developers
and managers who run software businesses that modify and/or redistribute
software under terms of the GNU GPL (or who wish to do so in the future),
and those who wish to make use of existing GPL'ed software in their
enterprise.

This tutorial introduces the GNU GPL and its terms to professionals who
are not well versed in the details of copyright law.  Presented by a
software developer and manager, this tutorial informs those who wish to
have a deeper understanding of how the GNU GPL uses copyright law to
protect software freedom and to assist in the formation of Free Software
businesses, and of the organizational motivations behind the GNU GPL.

Upon completion of the tutorial, successful attendees can expect to have
learned the following:

\begin{itemize}

  \item the freedom-defending purpose of each term of the GNU GPL.

  \item the redistribution options under the GPL.

  \item the obligations when modifying GPL'ed software.

  \item how to properly apply the GPL to a new software.

  \item how to build a plan for proper and successful compliance with the GPL.

  \item the business advantages that the GPL provides.

  \item the most common business models used in conjunction with the GPL.

  \item how existing GPL'ed software can be used in existing enterprises.
\end{itemize}

\end{abstract}

\tableofcontents

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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\chapter{What Is Free Software?}

Consideration of the GNU General Public License (herein, abbreviated as
\defn{GNU GPL} or just \defn{GPL}) must begin by first considering the broader
world of Free Software.  The GPL was not created from a void, rather,
it was created to embody and defend a set of principles that were set
forth at the founding of the GNU project and the Free Software Foundation
(FSF)---the organization that upholds, defends and promotes the philosophy
of software freedom.  A prerequisite for understanding the GPL and its
terms and conditions is a basic understanding of the principles behind it.
The GPL is unlike almost all other software licenses in that it is
designed to defend and uphold these principles.

\section{The Free Software Definition}
\label{Free Software Definition}

The Free Software Definition is set forth in full on FSF's website at
\href{http://www.fsf.org/philosophy/free-sw.html}{http://www.fsf.org/philosophy/free-sw.html}.
This section presents an abbreviated version that will focus on the parts
that are most pertinent to the terms of the GPL\@.

A particular program is Free Software if it grants a particular user of
that program, the following freedoms:

\begin{itemize}

\item the freedom to run the program for any purpose.

\item the freedom to change and modify the program.

\item the freedom to copy and share the program.

\item the freedom to share improved versions of the program.

\end{itemize}

The focus on ``a particular user'' is very pertinent here.  It is not
uncommon for the same version of a specific program to grant these
freedoms to some subset of its user base, while others have none or only
some of these freedoms.  Section~\ref{Proprietary Relicensing} talks in
detail about how this can happen even if a program is released under the
GPL\@.

Some people refer to software that gives these freedoms as ``Open
Source''.  Besides having a different political focus than those who call
it Free Software\footnote{The political differences between the Free
Software Movement and the Open Source Movement are documented on FSF's
website at
\href{http://www.fsf.org/philosophy/free-software-for-freedom.html}
{http://www.gnu.org/philosophy/free-software-for-freedom.html}.},
those who call the software ``Open Source'' are focused on a side issue.
User access to the source code of a program is a prerequisite to make use
of the freedom to modify.  However, the important issue is what freedoms
are granted in the license of that source code.  Microsoft's ``Shared
Source'' program, for example, gives various types of access to source
code, but almost none of the freedoms described in this section.

One key issue that is central to these freedoms is that there are no
restrictions on how these freedoms can be exercised.  Specifically, users
and programmers can exercise these freedoms non-commercially or
commercially.  Licenses that grant these freedoms for non-commercial
activities but prohibit them for commercial activities are considered
non-Free.

In general, software for which most or all of these freedoms are
restricted in any way is called ``non-Free Software''.  Typically, the
term ``proprietary software'' is used more or less interchangeably with
``non-Free Software''.  Personally, I tend to use the term ``non-Free
Software'' to refer to non-commercial software that restricts freedom
(such as ``shareware'') and ``proprietary software'' to refer to
commercial software that restricts freedom (such as nearly all of
Microsoft's and Oracle's offerings).

The remainder of this section considers each of the four freedoms in
detail.

\subsection{The Freedom to Run}

For a program to be Free Software, the freedom to run the program must be
completely unrestricted.  This means that any use for that software that
the user can come up with must be permitted.  Perhaps, for example, the
user has discovered an innovative new use for a particular program, one
that the programmer never could have predicted.  Such a use must not be
restricted.

It was once rare that this freedom was restricted by even proprietary
software; today it is not so rare.  Most End User Licensing Agreements
(EULAs) that cover most proprietary software restrict some types of use.
For example, some versions of Microsoft's FrontPage software prohibit use
of the software to create websites that generate negative publicity for
Microsoft.  Free Software has no such restrictions; everyone is free to
use Free Software for any purpose whatsoever.

\subsection{The Freedom to Change and Modify}

Free Software programs allow users to change, modify and adapt the
software to suit their needs.  Access to the source code and related build
scripts are an essential part of this freedom.  Without the source code
and the ability to build the binary applications from that source, the
freedom cannot be properly exercised.

Programmers can take direct benefit from this freedom, and often do.
However, this freedom is also important to users who are not programmers.
Users must have the right to exercise this freedom indirectly in both
commercial and non-commercial settings.  For example, users often seek
non-commercial help with the software on email lists and in users groups.
When they find such help, they must have the freedom to recruit
programmers who might altruistically assist them to modify their software.

The commercial exercise of this freedom is also essential for users.  Each
user, or group of users, must have the right to hire anyone they wish in a
competitive free market to modify and change the software.  This means
that companies have a right to hire anyone they wish to modify their Free
Software.  Additionally, such companies may contract with other companies
to commission software modification.

\subsection{The Freedom to Copy and Share}

Users may share Free Software in a variety of ways.  Free Software
advocates work to eliminate fundamental ethical dilemma of the software
age: choosing between obeying a software license, and friendship (by
giving away a copy of a program your friend who likes the software you are
using).  Free Software licenses, therefore, must permit this sort of
altruistic sharing of software among friends.

The commercial environment must also have the benefits of this freedom.
Commercial sharing typically takes the form of selling copies of Free
Software.  Free Software can be sold at any price to anyone.  Those who
redistribute Free Software commercially have the freedom to selectively
distribute (you can pick your customers) and to set prices at any level
the redistributor sees fit.

It is true that many people get copies of Free Software very cheaply (and
sometimes without charge). The competitive free market of Free Software
tends to keep prices low and reasonable.  However, if someone is willing
to pay a billion dollars for one copy of the GNU Compiler Collection, such
a sale is completely permitted.

Another common instance of commercial sharing is service-oriented
distribution.  For example, a distribution vendor may provide immediate
security and upgrade distribution via a special network service.  Such
distribution is completely permitted for Free Software.

(Section~\ref{Business Models} of this tutorial talks in detail about
various Free Software business models that take advantage of the freedom
to share commercially.)

\subsection{The Freedom to Share Improvements}

The freedom to modify and improve is somewhat empty without the freedom to
share those improvements.  The Free Software community is built on the
pillar of altruistic sharing of improved Free Software.  Inevitably, a
Free Software project sprouts a mailing list where improvements are shared
freely among members of the development community.  Such non-commercial
sharing must be permitted for Free Software to thrive.

Commercial sharing of modified Free Software is equally important.  For a
competitive free market for support to exist, all developers --- from
single-person contractors to large software companies --- must have the
freedom to market their services as improvers of Free Software.  All forms
of such service marketing must be equally available to all.

For example, selling support services for Free Software is fully
permitted.  Companies and individuals can offer themselves as ``the place
to call'' when software fails or does not function properly.  For such a
service to be meaningful, the entity offering that service must have the
right to modify and improve the software for the customer to correct any
problems that are beyond mere user error.

Entities must also be permitted to make available modified versions of
Free Software.  Most Free Software programs have a ``standard version''
that is made available from the primary developers of the software.
However, all who have the software have the ``freedom to fork'' --- that
is, make available non-trivial modified versions of the software on a
permanent or semi-permanent basis.  Such freedom is central to vibrant
developer and user interaction.

Companies and individuals have the right to make true value-added versions
of Free Software.  They may use freedom to share improvements to
distribute distinct versions of Free Software with different functionality
and features.  Furthermore, this freedom can be exercised to serve a
disenfranchised subset of the user community.  If the developers of the
standard version refuse to serve the needs of some of the software's
users, other entities have the right to create long- or short-lived fork
that serves that sub-community.

\section{How Does Software Become Free?}

The last section set forth the freedoms and rights are respected by Free
Software.  It presupposed, however, that such software exists.  This
section discusses how Free Software comes into existence.  But first, it
addresses how software can be non-free in the first place.

Software can be made proprietary only because it is governed by copyright
law\footnote{This statement is a bit of an oversimplification.  Patents
  and trade secrets can cover software and make it effectively non-free,
  one can contract away their rights and freedoms regarding software, or
  source code can be practically obscured in binary-only distribution
  without reliance on any legal system.  However, the primary control
  mechanism for software is copyright.}.  Copyright law, with respect to
software governs copying, modifying, and redistributing that
software\footnote{Copyright law in general also governs ``public
  performance'' of copyrighted works.  There is no generally agreed
  definition for public performance of software and version 2 of the GPL
  does not govern public performance.}.  By law, the copyright holder (aka
the author) of the work controls how others may copy, modify and/or
distribute the work.  For proprietary software, these controls are used to
prohibit these activities.  In addition, proprietary software distributors
further impede modification in a practical sense by distributing only
binary code and keeping the source code of the software secret.

Copyright law is a construction.  In the USA, the Constitution permits,
but does not require, the creation of copyright law as federal
legislation.  Software, since it is an idea fixed in a tangible medium, is
thus covered by the statues, and is copyrighted by default.

However, this legal construction is not necessarily natural.  Software, in
its natural state without copyright, is Free Software.  In an imaginary
world, which has no copyright, the rules would be different.  In this
world, when you received a copy of a program's source code, there would be
no default legal system to restrict you from sharing it with others,
making modifications, or redistributing those modified
versions\footnote{There could still exist legal systems, like our modern
  patent system, which could restrict the software in other ways.}.

Software in the real world is copyrighted by default, and that default
legal system does exist.  However, it is possible to move software out of
the domain of the copyright system.  A copyright holder is always
permitted to \defn{disclaim} their copyright.  If copyright is disclaimed,
the software is not governed by copyright law.  Software not governed by
copyright is in the ``public domain''.

\subsection{Public Domain Software}

An author can create public domain software by disclaiming all copyright
interest on the work.  In the USA and other countries that have signed the
Berne convention on copyright, software is copyrighted automatically by
the author when she ``fixes the software into a tangible medium''.  In
the software world, this usually means typing the source code of the
software into a file.

However, an author can disclaim that default control given to her by the
copyright laws.  Once this is done, the software is in the public domain
--- it is no longer covered by copyright.  Since it is copyright law that
allows for various controls on software (i.e., prohibition of copying,
modification, and redistribution), removing the software from the
copyright system and placing it into the public domain does yield Free
Software.

Carefully note that software in the public domain is \emph{not} licensed
in any way.  It is nonsensical to say software is ``licensed for the
public domain'', or any phrase that implies the copyright holder gave an
expressed permission to take actions governed by copyright law.

By contrast, what the copyright holder has done is renounce her copyright
controls on the work.  The law gave her controls over the work, and she
has chosen to waive those controls.  Software in the public domain is
absent copyright and absent a license.  The software freedoms discussed in
Section~\ref{Free Software Definition} are all granted because there is no
legal system in play to take them away.

\subsection{Why Copyright Free Software?}

If simply disclaiming copyright on software yields Free Software, then it
stands to reason that putting software into the public domain is the
easiest and most straightforward way to produce Free Software.  Indeed,
some major Free Software projects have chosen this method for making their
software Free.  However, most of the Free Software in existence \emph{is}
copyrighted.  In most cases (particularly in that of FSF and the GNU
Project), this was done due to very careful planning.

Software released into the public domain does grant freedom to those users
who receive the standard versions on which the original author disclaimed
copyright.  However, since the work is not copyrighted, any non-trivial
modification made to the work is fully copyrightable.

Free Software released into the public domain initially is Free, and
perhaps some who modify the software choose to place their work into the
public domain as well.  However, over time, some entities will choose to
proprietarize their modified versions.  The public domain body of software
feeds the proprietary software.  The public commons disappears, because
fewer and fewer entities have an incentive to contribute back to the
commons.  They know that any of their competitors can proprietarize their
enhancements.  Over time, almost no interesting work is left in the public
domain, because nearly all new work is done by proprietarization.

A legal mechanism is needed to redress this problem.  FSF was in fact
originally created primarily as a legal entity to defend software freedom,
and that work of of defending software freedom is a substantial part of
its work today.  Specifically because of this ``embrace, proprietarize and
extend'' cycle, FSF made a conscious choice to copyright its Free Software,
and then license it under ``copyleft'' terms, and many, including the
developers of the kernel named Linux have chosen to follow this paradigm.

Copyleft is a legal strategy to defend, uphold and propagate software
freedom.  The basic technique of copyleft is as follows: copyright the
software, license it under terms that give all the software freedoms, but
use the copyright law controls to ensure that all who receive a copy of
the software have equal rights and freedom.  In essence, copyleft grants
freedom, but forbids others to forbid that freedom from anyone else along
the distribution and modification chains.

Copyleft is a general concept.  Much like ideas for what a computer might
do must be \emph{implemented} by a program that actually does the job, so
too must copyleft be implemented in some concrete legal structure.
``Share and share alike'' is a phrase that is often enough to explain the
concept behind copyleft, but to actually make it work in the real world, a
true implementation in legal text must exist.  The GPL is the primary
implementation of copyleft in copyright licensing language.

\section{An Ecosystem of Equality}

The GPL uses copyright law to defend freedom and equally ensure users'
rights.  This ultimately creates an ecosystem of equality for both
business and non-commercial users.

\subsection{The Non-Commercial Ecosystem}

A GPL'ed code base becomes a center of a vibrant development and user
community.  Traditionally, volunteers, operating non-commercially out of
keen interest or ``scratch an itch'' motivations, produce initial versions
of a GPL'ed system.  Because of the efficient distribution channels of the
Internet, any useful GPL'ed system is adopted quickly by non-commercial
users.

Fundamentally, the early release and quick distribution of the software
gives birth to a thriving non-commercial community.  Users and developers
begin sharing bug reports and bug fixes across a shared intellectual
commons.  Users can trust the developers, because they know that if the
developers fail to address their needs or abandon the project, the GPL
ensures that someone else has the right to pick up development.
Developers know that the users cannot redistribute their software without
passing along the rights granted by GPL, so they are assured that every
one of their users is treated equally.

Because of the symmetry and fairness inherent in GPL'ed distribution,
nearly every GPL'ed package in existence has a vibrant non-commercial user
and developer base.

\subsection{The Commercial Ecosystem}

By the same token, nearly all established GPL'ed software systems have a
vibrant commercial community.  Nearly every GPL'ed system that has gained
wide adoption from non-commercial users and developers eventually begins
to fuel a commercial system around that software.

For example, consider the Samba file server system that allows Unix-like
systems (including GNU/Linux) to serve files to Microsoft Windows systems.
Two graduate students originally developed Samba in their spare time and
it was deployed non-commercially in academic environments.  However, very
soon for-profit companies discovered that the software could work for them
as well, and their system administrators began to use it in place of
Microsoft Windows NT file-servers.  This served to lower the cost of
ownership by orders of magnitude.  There was suddenly room in Windows
file-server budgets to hire contractors to improve Samba.  Some of the first
people hired to do such work were those same two graduate students who
originally developed the software.

The non-commercial users, however, were not concerned when these two
fellows began collecting paychecks off of their GPL'ed work.  They knew
that because of the nature of the GPL that improvements that were
distributed in the commercial environment could easily be folded back into
the standard version.  Companies are not permitted to proprietarize
Samba, so the non-commercial users, and even other commercial users are
safe in the knowledge that the software freedom ensured by GPL will remain
protected.

Commercial developers also work in concert with non-commercial developers.
Those two now-long-since graduated students continue to contribute to
Samba altruistically, but also get work doing it.  Priorities change when a
client is in the mix, but all the code is contributed back to the
standard version.  Meanwhile, many other individuals have gotten involved
non-commercially as developers, because they want to ``cut their teeth on
Free Software'' or because the problems interest them.  When they get good
at it, perhaps they will move on to another project or perhaps they will
become commercial developers of the software themselves.

No party is a threat to another in the GPL software scenario because
everyone is on equal ground.  The GPL protects rights of the commercial
and non-commercial contributors and users equally.  The GPL creates trust,
because it is a level playing field for all.

\subsection{Law Analogy}

In his introduction to Stallman's \emph{Free Software, Free Society},
Lawrence Lessig draws an interesting analogy between the law and Free
Software.  He argues that the laws of a Free society must be protected
much like the GPL protects software.  So that I might do true justice to
Lessig's argument, I quote it verbatim:

\begin{quotation}

A ``free society'' is regulated by law. But there are limits that any free
society places on this regulation through law: No society that kept its
laws secret could ever be called free. No government that hid its
regulations from the regulated could ever stand in our tradition. Law
controls.  But it does so justly only when visibly. And law is visible
only when its terms are knowable and controllable by those it regulates,
or by the agents of those it regulates (lawyers, legislatures).

This condition on law extends beyond the work of a legislature.  Think
about the practice of law in American courts.  Lawyers are hired by their
clients to advance their clients' interests. Sometimes that interest is
advanced through litigation. In the course of this litigation, lawyers
write briefs.  These briefs in turn affect opinions written by judges.
These opinions decide who wins a particular case, or whether a certain law
can stand consistently with a constitution.

All the material in this process is free in the sense that Stallman means.
Legal briefs are open and free for others to use.  The arguments are
transparent (which is different from saying they are good) and the
reasoning can be taken without the permission of the original lawyers.
The opinions they produce can be quoted in later briefs.  They can be
copied and integrated into another brief or opinion.  The ``source code''
for American law is by design, and by principle, open and free for anyone
to take. And take lawyers do---for it is a measure of a great brief that
it achieves its creativity through the reuse of what happened before.  The
source is free; creativity and an economy is built upon it.

This economy of free code (and here I mean free legal code) doesn't starve
lawyers.  Law firms have enough incentive to produce great briefs even
though the stuff they build can be taken and copied by anyone else.  The
lawyer is a craftsman; his or her product is public.  Yet the crafting is
not charity.  Lawyers get paid; the public doesn't demand such work
without price.  Instead this economy flourishes, with later work added to
the earlier.

We could imagine a legal practice that was different---briefs and
arguments that were kept secret; rulings that announced a result but not
the reasoning.  Laws that were kept by the police but published to no one
else.  Regulation that operated without explaining its rule.

We could imagine this society, but we could not imagine calling it
``free.''  Whether or not the incentives in such a society would be better
or more efficiently allocated, such a society could not be known as free.
The ideals of freedom, of life within a free society, demand more than
efficient application.  Instead, openness and transparency are the
constraints within which a legal system gets built, not options to be
added if convenient to the leaders.  Life governed by software code should
be no less.

Code writing is not litigation.  It is better, richer, more
productive. But the law is an obvious instance of how creativity and
incentives do not depend upon perfect control over the products created.
Like jazz, or novels, or architecture, the law gets built upon the work
that went before. This adding and changing is what creativity always is.
And a free society is one that assures that its most important resources
remain free in just this sense.\footnote{This quotation is Copyright
  \copyright{} 2002, Lawrence Lessig.  It is licensed under the terms of
  \href{http://creativecommons.org/licenses/by/1.0/}{the ``Attribution
    License'', version 1.0} or any later version as published by Creative
  Commons.}
\end{quotation}

In essence, lawyers are paid to service the shared commons of legal
infrastructure.  Few citizens defend themselves in court or write their
own briefs (even though they are legally permitted to do so) because
everyone would prefer to have an expert do that job.

The Free Software economy is a market that is ripe for experts.  It
functions similarly to other well established professional fields like the
law.  The GPL, in turn, serves as the legal scaffolding that permits the
creation of this vibrant commercial and non-commercial Free Software
economy.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\chapter{Copying, Modifying and Redistributing}

This chapter begins the deep discussion of the details of the terms of
GPL\@.  In this chapter, we consider the core terms: GPL \S\S 0--3.  These
are the sections of the GPL that fundamentally define the legal details of
how software freedom is respected.

\section{GPL \S 0: Freedom to Run}

\S 0, the opening section of GPL, sets forth that the work is governed by
copyright law.  It specifically points out that it is the ``copyright
holder'' who decides if a work is licensed under its terms, and explains
how the copyright holder might indicate this fact.

A bit more subtly, \S 0 makes an inference that copyright law is the only
system under which it is governed.  Specifically, it states:
\begin{quote}
Activities other than copying, distribution and modification are not
covered by this License; they are outside its scope.
\end{quote}
In essence, the license governs \emph{only} those activities and all other
activities are unrestricted, provided that no other agreements trump GPL
(which they cannot; see Sections~\ref{GPLs6} and~\ref{GPLs7}).  This is
very important, because the Free Software community heavily supports
users' rights to ``fair use'' and ``unregulated use'' of copyrighted
material.  GPL asserts through this clause that it supports users' rights
to fair and unregulated uses.

Fair use of copyrighted material is an established legal doctrine that
permits certain activities.  Discussion of the various types of fair use
activity are beyond the scope of this tutorial.  However, one important
example of fair use is the right to reverse engineering software.

Fair use is a doctrine established by the courts or by statute.  By
contrast, unregulated uses are those that are not covered by the statue
nor determined by a court to be covered, but are common and enjoyed by
many users.  An example of unregulated use is reading a program like a
novel for the purpose of learning how to be a better programmer.

\medskip

Thus, the GPL protects users fair and unregulated use rights precisely by
not attempting to cover them.  Furthermore, the GPL ensures the freedom
to run specifically by stating the following:
\begin{quote}
The act of running the Program is not restricted
\end{quote}
Thus, users are explicitly given the freedom to run by \S 0.

\medskip

The bulk of \S 0 not yet discussed gives definitions for other terms used
throughout.  The only one worth discussing in detail is ``work based on
the Program''.  The reason this definition is particularly interesting is
not for the definition itself, which is rather straightforward, but the
because it clears up a common misconception about the GPL\@.

The GPL is often mistakenly criticized because it fails to give a
definition of ``derivative work''.  In fact, it would be incorrect and
problematic if the GPL attempt to define this.  A copyright license, in
fact, has no control over what may or may not be a derivative work.  This
matter is left up to copyright law, not the licenses that utilize it.

It is certainly true that copyright law as a whole does not propose clear
and straightforward guidelines for what is and is not a derivative
software work under copyright law.  However, no copyright license --- not
even the GNU GPL -- can be blamed for this.  Legislators and court
opinions must give us guidance to decide the border cases.

\section{GPL \S 1: Verbatim Copying}

GPL \S 1 covers the matter of redistributing the source code of a program
exactly as it was received.  This section is quite straightforward.
However, there are a few details worth noting here.

The phrase ``in any medium'' is important.  This, for example, gives the
freedom to publish a book that is the printed copy of the program's source
code.  It also allows for changes in the medium of distribution.  Some
vendors may ship Free Software on a CD, but others may place it right on
the hard drive of a pre-installed computer.  Any such redistribution media
is allowed.

Preservation of copyright notice and license notifications are mentioned
specifically in \S 1.  These are in some ways the most important part of
the redistribution, which is why they are mentioned by name.  The GPL
always strives to make it abundantly clear to anyone who receives the
software what its license is.  The goal is to make sure users know their
rights and freedoms under GPL and to leave no reason that someone would be
surprised that the software she got was licensed under GPL\@.  Thus
throughout the GPL, there are specific reference to the importance of
notifying others down the distribution chain that they have rights under
GPL.

Also mentioned by name is the warranty disclaimer.  Most people today do
not believe that software comes with any warranty.  Notwithstanding the
proposed state-level UCITA bills (which have never obtained widespread
adoption), there are little or no implied warranties with software.
However, just to be on the safe side, GPL clearly disclaims them, and the
GPL requires redistributors to keep the disclaimer very visible.  (See
Sections~\ref{GPLs11} and~\ref{GPLs12} of this tutorial for more on GPL's
warranty disclaimers.)

Note finally that \S 1 begins to set forth the important defense of
commercial freedom.  \S 1 clearly states that in the case of verbatim
copies, one may make money.  Redistributors are fully permitted to charge
for the redistribution of copies of Free Software.  In addition, they may
provide the warranty protection that the GPL disclaims as an additional
service for a fee.  (See Section~\ref{Business Models} for more discussion
on making a profit from Free Software redistribution.)

\section{GPL \S 2: Share and Share Alike}

For many, this is where the ``magic'' happens that defends software
freedom along the distribution chain.  \S 2 is the only place in the GPL
that governs the modification controls of copyright law.  If someone
modifies a GPL'ed program, she is bound in the making those changes by \S
2.  The goal here is to ensure that the body of GPL'ed software, as it
continues and develops, remains Free as in freedom.

To achieve that goal, \S 2 first sets forth that the rights of
redistribution modified versions are the same as those for verbatim
copying, as presented in \S 1.  Therefore, the details of charging,
keeping copyright notices intact, and other \S 1 provisions are in tact
here as well.  However, there are three additional requirements.

The first (\S 2(a)) requires that modified files carry ``prominent
notices'' explaining what changes were made and the date of such changes.
The goal here is not to put forward some specific way of marking changes,
or controlling the process of how changes get made.  Primarily, \S 2(a)
seeks to ensure that those receiving modified versions know what path it
took to them.  For some users, it is important to know that they are using
the standard version of program, because while there are many advantages
to using a fork, there are a few disadvantages.  Users should be informed
the historical context of the software version they use, so that they can
make proper support choices.  Finally, \S 2(a) serves an academic purpose
--- ensuring that future developers can use a diachronic approach to
understand the software.

\medskip

The second requirement (\S 2(b)) contains the four short lines that embody
the legal details of ``share and share alike''.  These 46 words are
considered by some to be the most worthy of careful scrutiny.  It is worth
the effort to carefully understand what each clause is saying, because \S
2(b) can be a source of great confusion when not properly understood.

In considering \S 2(b), first note the qualifier: it only applies to
derivative works that ``you distribute or publish''.  Despite years of
education efforts by FSF on this matter, many still believe that modifiers
of GPL'ed software are required by the license to publish or otherwise
share their changes.  On the contrary, \S 2(b) {\bf does not apply if} the
changes are never distributed.  Indeed, the freedom to make private,
personal, unshared changes to software for personal use only should be
protected and defended\footnote{FSF does maintain that there is an {\bf
    ethical} obligation to redistribute changes that are generally useful,
  and often encourages companies and individuals to do so.  However, there
  is a clear distinction between what one {\bf ought} to do and what one
  {\bf must} do.}.

Next, we again encounter the same matter that appears in \S 0, in the
following text:
\begin{quote}
... that in whole or part contains or is derived from the Program or any
  part thereof,
\end{quote}
Again, the GPL relies here on what the copyright law says is a derivative
work.  If, under copyright law, the modified version ``contains or is
derived from'' the GPL'ed software, then the requirements of \S 2(b)
apply.  The GPL invokes its control as a copyright license over the
modification of the work in combination with its control over distribution
of the work.

The final clause of \S 2(b) describes what the licensee must do if she is
distributing or publishing a work that is deemed a derivative work under
copyright law --- namely, the following:
\begin{quote}
[The work must] be licensed as a whole at no charge to all third parties
under the terms of this License.
\end{quote}
That is probably the most tightly-packed phrase in all of the GPL\@.
Consider each subpart carefully.

The work ``as a whole'' is what is to be licensed.  This is an important
point that \S 2 spends an entire paragraph explaining; thus this phrase is
worthy of a lengthy discussion here.  As a programmer modifies a software
program, she generates new copyrighted material --- fixing expressions of
ideas into the tangible medium of electronic file storage.  That
programmer is indeed the copyright holder of those new changes.  However,
those changes are part and parcel to the original worked distributed to
the programmer under GPL\@.  Thus, the license of the original work
affects the license of the new whole derivative work.

% {\cal I}
\newcommand{\gplusi}{$\mathcal{G\!\!+\!\!I}$}
\newcommand{\worki}{$\mathcal{I}$}
\newcommand{\workg}{$\mathcal{G}$}

It is certainly possible to take an existing independent work (called
\worki{}) and combine it with a GPL'ed program (called \workg{}).  The
license of \worki{}, when it is distributed as a separate and independent
work, remains the prerogative of the copyright holder of \worki{}.
However, when \worki{} is combined with \workg{}, it produces a new work
that is the combination of the two (called \gplusi{}).  The copyright of
this derivative work, \gplusi{}, is jointly held by the original copyright
holder of each of the two works.

In this case, \S 2 lays out the terms by which \gplusi{} may be
distributed and copied.  By default, under copyright law, the copyright
holder of \worki{} would not have been permitted to distribute \gplusi{};
copyright law forbids it without the expressed permission of the copyright
holder of \workg{}.  (Imagine, for a moment, if \workg{} were a Microsoft
product --- would they give you permission to create and distribute
\gplusi{} without paying them a hefty sum?)  The license of \workg{}, the
GPL, sets forth ahead of time options for the copyright holder of \worki{}
who may want to create and distribute \gplusi{}.  This pre-granted
permission to create and distribute derivative works, provided the terms
of GPL are upheld, goes far above and beyond the permissions that one
would get with a typical work not covered by a copyleft license.  Thus, to
say that this restriction is any way unreasonable is simply ludicrous.

\medskip

The next phrase of note in \S 2(b) is ``licensed ... at no charge''.  This
is a source of great confusion to many.  Not a month goes by that FSF does
not receive an email that claims to point out ``a contradiction in GPL''
because \S 2 says that redistributors cannot charge for modified versions
of GPL'ed software, but \S 1 says that they can.  The ``at no charge''
means not that redistributors cannot charge for performing the acts
governed by copyright law\footnote{Recall that you could by default charge
  for any acts not governed by copyright law, because the license controls
  are confined by copyright.}, but rather that they cannot charge a fee
for the \emph{license itself}.  In other words, redistributors of
(modified and unmodified) GPL'ed works may charge any amount they choose
for performing the modifications on contract or the act of transferring
the copy to the customer, but they may not charge a separate licensing fee
for the software.

\S 2(b) further states that the software must ``be licensed ... to all
third parties''.  This too has led to some confusions, and feeds the
misconception mentioned earlier --- that all modified versions must made
available to the public at large.  However, the text here does not say
that.  Instead, it says that the licensing under terms of the GPL must
extend to anyone who might, through the distribution chain, receive a copy
of the software.  Distribution to all third parties is not mandated here,
but \S 2(b) does require redistributors to license the derivative works in
a way that is extends to all third parties who may ultimately receive a
copy of the software.

In summary, \S 2(b) says what terms under which the third parties must
receive this no-charge license.  Namely, they receive it ``under the terms
of this License'', the GPL.  When an entity \emph{chooses} to redistribute
a derivative work of GPL'ed software, the license of that whole derivative
work must be GPL and only GPL\@.  In this manner, \S 2(b) dovetails nicely
with \S 6 (as discussed in Section~\ref{GPLs6} of this tutorial).

\medskip

The final paragraph of \S 2 is worth special mention.  It is possible and
quite common to aggregate various software programs together on one
distribution medium.  Computer manufacturers do this when they ship a
pre-installed hard drive, and GNU/Linux distribution vendors do this to
give a one-stop CD or URL for a complete operating system with necessary
applications.  The GPL very clearly permits such ``mere aggregation'' with
programs under any license.  Despite what you hear from its critics, the
GPL is nothing like a virus, not only because the GPL is good for you and
a virus is bad for you, but also because simple contact with a GPL'ed
code-base does not impact the license of other programs.  Actual effort
must be expended by a programmer to cause a work to fall under the terms
of the GPL.  Redistributors are always welcome to simply ship GPL'ed
software alongside proprietary software or other unrelated Free Software,
as long as the terms of GPL are adhered to for those packages that are
truly GPL'ed.

\section{GPL \S 3: Producing Binaries}

% FIXME: need name of a novelist who writes very obscurely and obliquely.

Software is a strange beast when compared to other copyrightable works.
It is currently impossible to make a film or a book that can be truly
obscured.  Ultimately, the full text of a novel must presented to the
reader as words in some human-readable language so that they can enjoy the
work.  A film, even one directed by David Lynch, must be perceptible by
human eyes and ears to have any value.

Software is not so.  While the source code, the human-readable
representation of software is of keen interest to programmers, users and
programmers alike cannot make the proper use of software in that
human-readable form.  Binary code --- the ones and zeros that the computer
can understand --- must be predicable and attainable for the software to
be fully useful.  Without the binaries, be they in object or executable
form, the software serves only the didactic purposes of computer science.

Under copyright law, binary representations of the software are simply
derivative works of the source code.  Applying a systematic process (i.e.,
``compilation'') to a work of source code yields binary code.  The binary
code is now a new work of expression fixed in the tangible medium of
electronic file storage.

Therefore, for GPL'ed software to be useful, the GPL, since it governs the
rules for creation of derivative works, must grant permission for the
generation of binaries.  Furthermore, notwithstanding the relative
popularity of source-based GNU/Linux distributions like ``Gentoo'', users
find it extremely convenient to receive distribution of binary software.
Such distribution is the redistribution of derivative works of the
software's source code.  \S 3 addresses the matter of creation and
distribution of binary versions.

Under \S 3, binary versions may be created and distributed under the terms
of \S\S 1--2, so all the material previously discussed applies here.
However, \S 3 must go a bit further.  Access to the software's source code
is an incontestable prerequisite for the exercise of the fundamental
freedoms to modify and improve the software.  Making even the most trivial
changes to a software program at the binary level is effectively
impossible.  \S 3 must ensure that the binaries are never distributed
without the source code, so that these freedoms are ensured to be passed
along the distribution chain.

\S 3 permits distribution of binaries, and then offers three options for
distribution of source code along with binaries.  The most common and the
least complicated is the option given under \S 3(a).

\S 3(a) offers the option to directly accompany the source code alongside
the distribution of the binaries.  This is by far the most convenient
option for most distributors, because it means that the source-code
provision obligations are fully completed at the time of binary
distribution (more on that later).

Under \S 3(a), the source code code provided must be the ``corresponding
source code''.  Here ``corresponding'' primarily means that the source
code provided must be that code used to produce the binaries being
distributed.  That source code must also be ``complete''.  A later
paragraph of \S 3 explains in detail what is meant by ``complete''.  In
essence, it is all the material that a programmer of average skill would
need to actually use the source code to produce the binaries she has
received.  Complete source is required so that, if the licensee choses,
she should be able to exercise her freedoms to modify and redistribute
changes.  Without the complete source, it would not be possible to make
changes that were actually directly derived from the version received.

Furthermore, \S 3 is defending against a tactic that has in fact been seen
in FSF's GPL enforcement.  Under GPL, if you pay a high price for a copy
of GPL'ed binaries (which comes with corresponding source, of course), you
have the freedom to redistribute that work at any fee you choose, or not
at all.  Sometimes, companies attempt to build a racket by producing very
specialized binaries (perhaps for an obscure architecture), and then
giving source code that does correspond, but not giving the
``incantations'' and build plans they used to make that source compile
into the specialized binaries.  Therefore, \S 3 that the source code
include ``meta-material'' like scripts, interface definitions, and other
material that is used to ``control compilation and installation'' of the
binaries.  In this manner, those further down the distribution chain are
assured that they have the unabated freedom to build their own derivative
works from the sources provided.

FSF (as authors of GPL) realizes that software distribution comes in many
forms.  Embedded manufacturers, for example, have the freedom to put
GPL'ed software into their PDAs with very tight memory and space
constraints.  In such cases, putting the source right alongside the
binaries on the machine itself might not be an option.  While it is
recommended that this be the default way that people comply with GPL, the
GPL does provide options when such distribution is infeasible.

\S 3, therefore, allows source code to be provided on any physical
``medium customarily used for software interchange''.  By design, this
phrase covers a broad spectrum.  At best, FSF can viably release a new GPL
every ten years or so.  Thus, phrases like this must be adaptive to
changes in the technology.  When GPL version 2 was first published in June
1991, distribution on magnetic tape was still common, and CD was
relatively new.  Today, CD is the default, and for larger systems DVD-ROM
is gaining adoption.  This language must adapt with changing technology.

Meanwhile, the binding created by the word ``customarily'' is key.  Many
incorrectly believe that distributing binary on CD and source on the
Internet is acceptable.  In the corporate world, it is indeed customary to
simply download CDs worth of data over a T1 or email large file
attachments.  However, even today in the USA, many computer users with
CD-ROM drives are not connected to the Internet, and most people connected
to the Internet are connected via a 56K dial-up connection.  Downloading
CDs full of data is not customary for them in the least.  In some cities
in Africa, computers are becoming more common, but Internet connectivity
is still available only at a few centralized locations.  Thus, the
``customs'' here have must have a worldwide scope in context, and simply
providing source on the Internet --- while it is a kind, friendly and
useful thing to do --- is not usually sufficient.

Note, however, a major exception to this rule, given by the last paragraph
of \S 3.  \emph{If} distribution of the binary files is made only on the
Internet (i.e., ``from a designated place''), \emph{then} simply providing
the source code right alongside the binaries in the same place is
sufficient to comply with \S 3.

\medskip

As is shown above, Under \S 3(a), embedded manufacturers can put the
binaries on the device and ship the source code along on a CD\@.  However,
sometimes this turns out to be too costly.  Including a CD with every
device could prove too costly, and may practically (although not legally)
prohibit using GPL'ed software.  For this situation and others like it, \S
3(b) is available.

\S 3(b) allows a distributor of binaries to instead provide a written
offer for source code alongside those binaries.  This is useful in two
specific ways.  First, it may turn out that most users do not request the
source, and thus the cost of producing the CDs is saved --- a financial
and environmental windfall.  In addition, along with a \S 3(b) compliant
offer for source, a binary distributor might choose to \emph{also} give a
URL for source code.  Many who would otherwise need a CD with source might
turn out to have those coveted high bandwidth connections, and are able to
download the source instead --- again yielding environmental and financial
windfalls.

However, note that regardless of how many users prefer to get the source
online, that \S 3(b) does place lasting long-term obligations on the
binary distributor.  The binary distributor must be prepared for three
years to honor that offer for source, and ship it out (just as they would
have had to do under \S 3(a)) at a moment's notice when they receive such
a request.  There is real organizational cost here: support engineers for
three years must be trained how to route source requests, and source CD
images for every release version for the last three years must be kept on
hand to burn such CDs quickly.  The requests might not even come from
actual customers; the offer for source must be valid for ``any third
party''.

That phrase is another place where some get confused --- thinking again
that full public distribution of source is required.  The offer for source
must be valid for ``any third party'' because of the freedoms of
redistribution granted by \S\S 1--2.  A company may ship a binary image
and an offer for source to only one customer.  However, under GPL, that
customer has the right to redistribute that software to the world if she
likes.  When she does, that customer has an obligation to make sure that
those who receive the software from her can exercise their freedoms under
GPL --- including the freedom to modify, rebuild, and redistribute the
source code.

This is where \S 3(c) comes into play.  Ultimately, \S 3(b) is a big
compromise.  It separates the binary software from the key tool that
people can use to exercise their freedom.  The GPL permits this separation
because it is good for redistributors, and those users who turn out not to
need the source.  However, to ensure equal rights for all software users,
anyone along the distribution chain must have the right to get the source
and exercise those freedoms that require it.

Meanwhile, \S 3(b)'s compromise primarily benefits companies who
distribute binary software commercially.  Without \S 3(c), that benefit
would be at the detriment of the companies' customers; the burden of
source code provision would be unfairly shifted to the companies'
customers.  A customer, who had received binaries with a \S 3(b)-compliant
offer, would be required under GPL (sans \S 3(c)) to acquire the source,
merely to give a copy of the software to a friend who needed it.  \S 3(c)
reshifts this burden to entity who benefits from \S 3(b).

\S 3(c) allows those who undertake \emph{non-commercial} distribution to
simply pass along a \S 3(b)-compliant source code offer.  The customer who
wished to give a copy to her friend can now do so without provisioning the
source, as long as she gives that offer to her friend.  By contrast, if
she wanted to go into business for herself selling CDs of that software,
she would have to acquire the source and either comply via \S 3(a), or
write her own \S 3(b)-compliant source offer.

This process is precisely the reason why a \S 3(b) source offer must be
valid for all third parties.  At the time the offer is made, there is no
way of knowing who might end up non-commercially receiving a copy of the
software.  Companies who choose to comply via \S 3(b) must thus be
prepared to honor all incoming source code requests.  For this and the
many other additional necessary complications under \S\S 3(b--c), it is
only rarely a better option than complying via \S 3(a).


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\chapter{Defending Freedom On Many Fronts}

The last chapter presented the core freedom-defending provisions of GPL\@,
which are in \S\S 0--3.  \S\S 4--7 of the GPL are designed to ensure that
\S\S 0--3 are not infringed, are enforceable, are kept to the confines of
copyright law and are not trumped by other copyright agreements or
components of other entirely separate legal systems.  In short, while \S\S
0--3 are the parts of the license that defend the freedoms of users and
programmers, \S\S 4--7 are the parts of the license that keep the playing
field clear so that \S\S 0--3 can do their jobs.

\section{GPL \S 4: Termination on Violation}
\label{GPLs4}

\S 4--5 are, in my opinion, the heart of the GPL\@. \S\S 0--3 are
important in their efforts to set forth in clear legal language the
doctrine of copyleft.  However, \S 4--5 are the glue that holds \S\S 0--3
together.

\S 4 is GPL's termination clause.  Upon first examination, it seems
strange for a license that has the goal of defending users and programmers
freedoms for perpetuity in an irrevocable way would have such a clause.
However, upon further examination, the difference between irrevocability
and this termination clause becomes clear.

The GPL is irrevocable in the sense that once a copyright holder grants
rights for someone to copy, modify and redistribute the software under
terms of the GPL, they cannot later revoke that grant.  Since the GPL has
no provision allowing the copyright holder to take such a prerogative, the
license is granted as long as the copyright remains in effect\footnote{In
  the USA< due to unfortunate legislation, this is nearly perpetual, even
  though the Constitution forbids it.}.  The copyright holder has the
right to relicense the same work under different licenses (see
Section~\ref{Proprietary Relicensing} of this tutorial), or to stop
distributing the GPL'ed version (assuming \S 3(b) was never used), but the
she may not revoke the rights under GPL already granted.

In fact, when an entity looses their right to copy, modify and distribute
GPL'ed software, it is because of their \emph{own actions}, not that of
the copyright holder.  The copyright holder does not decided when \S 4
termination occurs (if ever), the actions of the licensee does.

Under copyright law, the GPL has granted various rights and freedoms to
the licensee to perform specific types of copying, modification, and
redistribution.  By default, all other types of copying, modification, and
redistribution are prohibited.  \S 4 says that if you undertake any of
those other types (e.g., redistributing binary-only in violation of \S 3),
then all rights under the license --- even those otherwise permitted for
those who have not violated --- terminate automatically.

\S 4 gives GPL teeth.  If licensees fail to adhere to the license, then
they are stuck.  They must to completely cease and desist from all
copying, modification and distribution of that GPL'ed software.

At that point, violating licensees must gain the forgiveness of the
copyright holder to have their rights restored.  Alternatively, they could
negotiate another agreement, separate from GPL, with the copyright
holder.  Both are common practice.

At FSF, it is part of the mission to spread software freedom.  When FSF
enforces GPL, the goal is to bring the violator back into compliance as
quickly as possible, and redress the damage caused by the violation.
That is FSF's steadfast position in a violation negotiation --- comply
with the license and respect freedom.

However, other entities who do not share the full ethos of software
freedom as institutionalized by FSF pursue GPL violations differently.  MySQL
AB, a company that produces the GPL'ed MySQL database, upon discovering
GPL violations typically negotiates a proprietary software license
separately for a fee.  While this practice is not one that FSF would ever
consider undertaking or even endorsing, it is a legal way for copyright
holders to proceed.

\section{GPL \S 5: Acceptance, Copyright Style}
\label{GPLs5}

\S 5 brings us to perhaps the most fundamental misconception and common
confusion about GPL\@.  Because of the prevalence of proprietary software,
most users, programmers, and lawyers alike tend to be more familiar with
EULAs.  EULAs are believed by their authors to be contracts, requiring
formal agreement between the licensee and the software distributor to be
valid.  This has led to mechanisms like ``shrink-wrap'' and ``click-wrap''
as mechanisms to perform acceptance ceremonies with EULAs.

The GPL does not need contract law to ``transfer rights''.  No rights are
transfered between parties.  By contrast, the GPL is permission slip to
undertake activities that would otherwise been prohibited by copyright law.
As such, it needs no acceptance ceremony; the licensee is not even
required to accept the license.

However, without the GPL, the activities of copying, modifying and
distributing the software would have otherwise been prohibited.  So, the
GPL says that you only accepted the license by undertaking activities that
you would have otherwise been prohibited without your license under GPL\@.
This is a certainly subtle point, and requires a mindset quite different
from the contractual approach taken by EULA authors.

An interesting side benefit to \S 5 is that the bulk of users of Free
Software are not required to accept the license.  Undertaking fair and
unregulated use of the work, for example, does not bind you to the GPL,
since you are not engaging in activity that is otherwise controlled by
copyright law.  Only when you engage in those activities that might have an
impact on the freedom of others does license acceptance occur and the
terms begin to bind you to fair and equitable sharing of the software.  In
other words, the GPL only kicks in when it needs to for the sake of
freedom.

\section{GPL \S 6: GPL, My One and Only}
\label{GPLs6}

A point that was glossed over in Section~\ref{GPLs4}'s discussion of \S 4
was the irrevocable nature of the GPL\@.  The GPL is indeed irrevocable,
and it is made so formally \S 6.

The first sentence in \S 6 ensures that as software propagates down the
distribution chain, that each licensor can pass along the license to each
new licensee.  Under \S 6, the act of distributing automatically grants a
license from the original licensor to the next recipient.  This creates a
chain of grants that ensure that everyone in the distribution has rights
under the GPL\@.  In a mathematical sense, this bounds the bottom ---
making sure that future licensees get no fewer rights than than the
licensee before.

The second sentence of \S 6 does the opposite; it bounds from the top.  It
prohibits any licensor along the distribution chain from placing
additional restrictions on the user.  In other words, no additional
requirements may trump the rights and freedoms given by GPL\@.

The final sentence of \S 6 makes it abundantly clear that no individual
entity in the distribution chain is responsible for the compliance of any
other.  This is particularly important for non-commercial users who have
passed along a source offer under \S 3(c), as they cannot be assured that
the issuer of the offer will honor their \S 3 obligations.

In short, \S 6 says that your license for the software is your one and
only copyright license allowing you to copy, modify and distribute the
software.

\section{GPL \S 7: ``Give Software Liberty of Give It Death!''}
\label{GPLs7}

In essence, \S 7 is a verbosely worded way of saying for non-copyright
systems what \S 6 says for copyright.  If there exists any reason that a
distributor knows of that would prohibit later licensees from exercising
their full rights under GPL, then distribution is prohibited.

Originally, this was designed as the title of this section suggests --- as
a last ditch effort to make sure that freedom was upheld.  However, in
modern times, it has come to give much more.  Now that the body of GPL'ed
software is so large, patent holders who would want to be distributors of
GPL'ed software have a tough choice.  They must choose between avoiding
distribution of GPL'ed software that exercises the teachings of their
patents, or grant a royalty-free, irrevocable, non-exclusive license to
those patents.  Many companies, including IBM, the largest patent holder
in the world, have chosen the latter.

Thus, \S 7 is rarely gives software death by stopping its distribution.
Instead, it is inspiring patent holders to share their patents in the same
freedom-defending way that they share their copyrighted works.

\section{GPL \S 8: Excluding Unfreedonia}
\label{GPLs8}

\S 8 is rarely used by copyright holders.  Its intention is that, if
particular country, say Unfreedonia, grant particular patents or allow
copyrighted interfaces (no country to our knowledge even permits those
yet), that the GPL'ed software can continue in free and unabated
distribution in the countries where such controls do not exist.

It is a partial ``out'' from \S 7.  Without \S 8, if a copyright holder
knew of a patent in a particular country licensed in a GPL-incompatible
way, then she could not distribute under GPL, because the work would
legitimately end up in the hands of citizens of Unfreedonia.

It is an inevitable but sad reality that some countries are freer than
others.  \S 8 exists to permit distribution on those countries that are
free without otherwise negating parts of the license.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\chapter{Odds, Ends, and Absolutely No Warranty}

\S 0--7 constitute the freedom-defending terms of the GPL.  The balance
of the GPL handles administrivia and issues concerning warranties and
liability.

\section{GPL \S 9: FSF as stewards of GPL}
\label{GPLs9}

FSF reserves the exclusive right to publish future versions of the GPL\@;
\S 9 expresses this.  While the stewardship of the copyrights on the body
of GPL'ed software around the world is shared among thousands of
individuals and organizations, the license itself needs a single steward.
Forking of the code is often regrettable but basically innocuous.  Forking
of licensing is disastrous.

FSF has only released two versions of GPL --- in 1989 and 1991.  GPL,
version 3, is under current internal drafting.  FSF's plan is to have a
long and engaging comment period.  The goal of GPL is defend freedom, and
a gigantic community depends on that freedom now.  FSF hopes to take all
stakeholders' opinions under advisement.

\section{GPL \S 10: Relicensing Permitted}
\label{GPLs10}

\S 10 reminds the licensee of what is already implied by the nature of
copyright law.  Namely, the copyright holder of a particular software
program has the prerogative to grant alternative agreements under separate
copyright licenses.

\section{GPL \S 11: No Warranty}
\label{GPLs11}

With \S 11, the boilerplate language of all copyright licenses begins.
Sometimes, companies are concerned that there is no default warranty on
GPL'ed software.  However, nearly all proprietary software licensing
agreements disclaim warranty as well.

All warranty disclaimer language tends to be shouted in all capital
letters.  Apparently, there was once a case where the disclaimer language
of an agreement was negated because it was not ``conspicuous'' to one of
the parties.  Therefore, to make such language ``conspicuous'', people
started placing it in bold or capitalizing the entire text.  It now seems
to be voodoo tradition of warranty disclaimer writing.

Finally, one important point to remember when reading \S 11 is that \S 1
permits the sale of warranty as an additional service, which  \S 11
affirms.

\section{GPL, \S 12: Limitation of Liability}
\label{GPLs12}

There are many types of warranties, and in some jurisdictions some of them
cannot be disclaimed.  Therefore, usually agreements will have both a
warranty disclaimer and a limitation of liability, as we have in \S 12.
\S 11 thus gets rid of all implied warranties that can legally be
disavowed.  \S 12, in turn, limits the liability of the actor for any
warranties that cannot legally be disclaimed in a particular jurisdiction.

So ends the terms and conditions of the GNU General Public License.


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\chapter{Integrating the GPL into Business Practices}

Since GPL'ed software is now extremely prevalent through the industry, it
is useful to has some basic knowledge about using GPL'ed software in
business and how to build business models around GPL'ed software.

\section{Using GPL'ed Software In-House}

A discussed in Sections~\ref{GPLs0} and~\ref{GPLs5} of this tutorial, the
GPL only governs the activities of copying, modifying and distributing the
software are not governed by the license.  Thus, in FSF's view, simply
installing the software on a machine and using it is not controlled or
limited in any way by GPL\@.  Using Free Software in general requires
substantially fewer agreements and less license compliance activity than
any known proprietary software.

Even if a company engages heavily in copying the software throughout the
enterprise, such copying is not only permitted by \S\S 1 and 3, but it is
encouraged!  If the company simply deploy unmodified (or even modified)
Free Software throughout the organization for its employees to use, the
obligations under the license are very minimal.  Using Free Software has a
substantially lower cost of ownership --- both in licensing fees and in
licensing checking and handling -- than the proprietary software
equivalents.

\section{Business Models}
\label{Business Models}

Using Free Software in house is certainly helpful, but there is also a
thriving market for Free Software-oriented business models.  There is the
traditional model of selling copies of Free Software distributions.  Many
companies, including IBM and Red Hat, make substantial revenue from this
model.  IBM primarily chooses this model because they have found that for
higher-end hardware, the cost of the profit made from proprietary software
licensing fees is negligible.  The real profit is in the hardware, but it is
essential that software be stable, reliable and dependable, and the users
be allowed to have unfettered access to it.  Free Software, and GPL'ed
software in particular (because IBM can be assured that proprietary
versions of the same software will not exists to compete on their
hardware) is the right choice.

Red Hat has actually found that a ``convenience fee'' for Free Software,
when set at a reasonable price (around \$60 or so), can produce some
profit.  Even though Red Hat's system is fully downloadable on their
website, people still go to local computer stores and buy copies of their
box set, which is simply a printed version of the manual (available under
a free license as well) and the Free Software system it documents.

\medskip

However, custom support, service, and software improvement contracts are
the most widely used models for GPL'ed software.  The GPL is central to
their success, because it ensure that the code base remains common, and
that large and small companies are on equal footing for access to the
technology.  Consider, for example, the GNU Compiler Collection (GCC).
Cygnus Solutions, a company started in the early 1990s, was able to grow
steadily simply by providing services for GCC --- mostly consisting of
porting GCC to new embedded chipset target platforms.  Eventually, Cygnus
was so successful that it was purchased by Red Hat where it remains a
profitable division.

However, there are very small companies like CodeSourcery, as well as
other medium sized companies like MontaVista and OpenTV that compete in
this space.  Because the code-base is protect by GPL, it creates and
demands industry trust.  Companies can cooperate on the software and
improve it for everyone.  Meanwhile, companies who rely on GCC for their
work are happy to pay for improvements, and for ports to new target
platforms, and nearly all the changes fold back into the standard
versions, and those forks that exist remain freely available.

\medskip

\label{Proprietary Relicensing}

A final common business model that is perhaps the most controversial is
proprietary relicensing of a GPL'ed code base.  This is only an option for
software in which a particular entity is the sole copyright holder.  As
discussed earlier in this tutorial, a copyright holder is permitted under
copyright law to license a software system under her copyright as many
different ways as she likes to as many different parties as she wishes.

Some companies, such as MySQL AB and TrollTech, use this to their
financial advantage with regard to a GPL'ed code base.  The standard
version is available from the company under the terms of the GPL\@.
However, parties can purchase separate proprietary software licensing for
a fee.

This business model is problematic because it means that the GPL'ed code
base must be developed in a somewhat monolithic way, because volunteer
Free Software developers may be reluctant to assign their copyrights to
the company because it will not promise to always and forever license the
software as Free Software.  Indeed, the company will surely use such code
contributions in proprietary versions licensed for fees.

\section{Ongoing Compliance}

GPL compliance is in fact a very simple matter -- much simpler than
typical proprietary software agreements and EULAs.  Usually, the most
difficult hurdle is changing from a proprietary software mindset to one
that seeks to foster a community of sharing and mutual support.  Certainly
complying with the GPL from a users' perspective gives substantially fewer
headaches than proprietary license compliance.

For those who go into the business of distributing or distributing
modified versions of GPL'ed software, the burden is a bit higher, but not
by much.  The glib answer that is that it is always easy to comply with
the GPL by releasing the whole product as Free Software.  However,
admittedly to the chagrin of FSF, many modern and complex software systems
are built using both proprietary and GPL'ed components that are not
legally derivative works of each other.  Usually, in product development
with Free Software tools, sometimes it is easier simply to improve
existing GPL'ed application than to start from scratch.  In exchange for
that benefit, the license requires that the modifier give back to the
commons that made the work easier.  It is a reasonable trade-off, and it
is a way to help build a better world while also making a profit.

Note that FSF does provide services to assist companies who need
assistance in complying with the GPL.  You can contact FSF's GPL
Compliance Labs at <compliance@fsf.org>.

\appendix

\chapter{The GNU General Public License}

\begin{center}
{\parindent 0in

Version 2, June 1991

Copyright \copyright\ 1989, 1991 Free Software Foundation, Inc.

\bigskip

59 Temple Place - Suite 330, Boston, MA  02111-1307, USA

\bigskip

Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
}
\end{center}

\begin{center}
{\bf\large Preamble}
\end{center}


The licenses for most software are designed to take away your freedom to
share and change it.  By contrast, the GNU General Public License is
intended to guarantee your freedom to share and change free software---to
make sure the software is free for all its users.  This General Public
License applies to most of the Free Software Foundation's software and to
any other program whose authors commit to using it.  (Some other Free
Software Foundation software is covered by the GNU Library General Public
License instead.)  You can apply it to your programs, too.

When we speak of free software, we are referring to freedom, not price.
Our General Public Licenses are designed to make sure that you have the
freedom to distribute copies of free software (and charge for this service
if you wish), that you receive source code or can get it if you want it,
that you can change the software or use pieces of it in new free programs;
and that you know you can do these things.

To protect your rights, we need to make restrictions that forbid anyone to
deny you these rights or to ask you to surrender the rights.  These
restrictions translate to certain responsibilities for you if you
distribute copies of the software, or if you modify it.

For example, if you distribute copies of such a program, whether gratis or
for a fee, you must give the recipients all the rights that you have.  You
must make sure that they, too, receive or can get the source code.  And
you must show them these terms so they know their rights.

We protect your rights with two steps: (1) copyright the software, and (2)
offer you this license which gives you legal permission to copy,
distribute and/or modify the software.

Also, for each author's protection and ours, we want to make certain that
everyone understands that there is no warranty for this free software.  If
the software is modified by someone else and passed on, we want its
recipients to know that what they have is not the original, so that any
problems introduced by others will not reflect on the original authors'
reputations.

Finally, any free program is threatened constantly by software patents.
We wish to avoid the danger that redistributors of a free program will
individually obtain patent licenses, in effect making the program
proprietary.  To prevent this, we have made it clear that any patent must
be licensed for everyone's free use or not licensed at all.

The precise terms and conditions for copying, distribution and
modification follow.

\begin{center}
{\Large \sc Terms and Conditions For Copying, Distribution and
  Modification}
\end{center}


%\renewcommand{\theenumi}{\alpha{enumi}}
\begin{enumerate}

\addtocounter{enumi}{-1}

\item

This License applies to any program or other work which contains a notice
placed by the copyright holder saying it may be distributed under the
terms of this General Public License.  The ``Program'', below, refers to
any such program or work, and a ``work based on the Program'' means either
the Program or any derivative work under copyright law: that is to say, a
work containing the Program or a portion of it, either verbatim or with
modifications and/or translated into another language.  (Hereinafter,
translation is included without limitation in the term ``modification''.)
Each licensee is addressed as ``you''.

Activities other than copying, distribution and modification are not
covered by this License; they are outside its scope.  The act of
running the Program is not restricted, and the output from the Program
is covered only if its contents constitute a work based on the
Program (independent of having been made by running the Program).
Whether that is true depends on what the Program does.

\item You may copy and distribute verbatim copies of the Program's source
  code as you receive it, in any medium, provided that you conspicuously
  and appropriately publish on each copy an appropriate copyright notice
  and disclaimer of warranty; keep intact all the notices that refer to
  this License and to the absence of any warranty; and give any other
  recipients of the Program a copy of this License along with the Program.

You may charge a fee for the physical act of transferring a copy, and you
may at your option offer warranty protection in exchange for a fee.

\item

You may modify your copy or copies of the Program or any portion
of it, thus forming a work based on the Program, and copy and
distribute such modifications or work under the terms of Section 1
above, provided that you also meet all of these conditions:

\begin{enumerate}

\item

You must cause the modified files to carry prominent notices stating that
you changed the files and the date of any change.

\item

You must cause any work that you distribute or publish, that in
whole or in part contains or is derived from the Program or any
part thereof, to be licensed as a whole at no charge to all third
parties under the terms of this License.

\item
If the modified program normally reads commands interactively
when run, you must cause it, when started running for such
interactive use in the most ordinary way, to print or display an
announcement including an appropriate copyright notice and a
notice that there is no warranty (or else, saying that you provide
a warranty) and that users may redistribute the program under
these conditions, and telling the user how to view a copy of this
License.  (Exception: if the Program itself is interactive but
does not normally print such an announcement, your work based on
the Program is not required to print an announcement.)

\end{enumerate}


These requirements apply to the modified work as a whole.  If
identifiable sections of that work are not derived from the Program,
and can be reasonably considered independent and separate works in
themselves, then this License, and its terms, do not apply to those
sections when you distribute them as separate works.  But when you
distribute the same sections as part of a whole which is a work based
on the Program, the distribution of the whole must be on the terms of
this License, whose permissions for other licensees extend to the
entire whole, and thus to each and every part regardless of who wrote it.

Thus, it is not the intent of this section to claim rights or contest
your rights to work written entirely by you; rather, the intent is to
exercise the right to control the distribution of derivative or
collective works based on the Program.

In addition, mere aggregation of another work not based on the Program
with the Program (or with a work based on the Program) on a volume of
a storage or distribution medium does not bring the other work under
the scope of this License.

\item
You may copy and distribute the Program (or a work based on it,
under Section 2) in object code or executable form under the terms of
Sections 1 and 2 above provided that you also do one of the following:

\begin{enumerate}

\item

Accompany it with the complete corresponding machine-readable
source code, which must be distributed under the terms of Sections
1 and 2 above on a medium customarily used for software interchange; or,

\item

Accompany it with a written offer, valid for at least three
years, to give any third party, for a charge no more than your
cost of physically performing source distribution, a complete
machine-readable copy of the corresponding source code, to be
distributed under the terms of Sections 1 and 2 above on a medium
customarily used for software interchange; or,

\item

Accompany it with the information you received as to the offer
to distribute corresponding source code.  (This alternative is
allowed only for noncommercial distribution and only if you
received the program in object code or executable form with such
an offer, in accord with Subsection b above.)

\end{enumerate}


The source code for a work means the preferred form of the work for
making modifications to it.  For an executable work, complete source
code means all the source code for all modules it contains, plus any
associated interface definition files, plus the scripts used to
control compilation and installation of the executable.  However, as a
special exception, the source code distributed need not include
anything that is normally distributed (in either source or binary
form) with the major components (compiler, kernel, and so on) of the
operating system on which the executable runs, unless that component
itself accompanies the executable.

If distribution of executable or object code is made by offering
access to copy from a designated place, then offering equivalent
access to copy the source code from the same place counts as
distribution of the source code, even though third parties are not
compelled to copy the source along with the object code.

\item
You may not copy, modify, sublicense, or distribute the Program
except as expressly provided under this License.  Any attempt
otherwise to copy, modify, sublicense or distribute the Program is
void, and will automatically terminate your rights under this License.
However, parties who have received copies, or rights, from you under
this License will not have their licenses terminated so long as such
parties remain in full compliance.

\item
You are not required to accept this License, since you have not
signed it.  However, nothing else grants you permission to modify or
distribute the Program or its derivative works.  These actions are
prohibited by law if you do not accept this License.  Therefore, by
modifying or distributing the Program (or any work based on the
Program), you indicate your acceptance of this License to do so, and
all its terms and conditions for copying, distributing or modifying
the Program or works based on it.

\item
Each time you redistribute the Program (or any work based on the
Program), the recipient automatically receives a license from the
original licensor to copy, distribute or modify the Program subject to
these terms and conditions.  You may not impose any further
restrictions on the recipients' exercise of the rights granted herein.
You are not responsible for enforcing compliance by third parties to
this License.

\item
If, as a consequence of a court judgment or allegation of patent
infringement or for any other reason (not limited to patent issues),
conditions are imposed on you (whether by court order, agreement or
otherwise) that contradict the conditions of this License, they do not
excuse you from the conditions of this License.  If you cannot
distribute so as to satisfy simultaneously your obligations under this
License and any other pertinent obligations, then as a consequence you
may not distribute the Program at all.  For example, if a patent
license would not permit royalty-free redistribution of the Program by
all those who receive copies directly or indirectly through you, then
the only way you could satisfy both it and this License would be to
refrain entirely from distribution of the Program.

If any portion of this section is held invalid or unenforceable under
any particular circumstance, the balance of the section is intended to
apply and the section as a whole is intended to apply in other
circumstances.

It is not the purpose of this section to induce you to infringe any
patents or other property right claims or to contest validity of any
such claims; this section has the sole purpose of protecting the
integrity of the free software distribution system, which is
implemented by public license practices.  Many people have made
generous contributions to the wide range of software distributed
through that system in reliance on consistent application of that
system; it is up to the author/donor to decide if he or she is willing
to distribute software through any other system and a licensee cannot
impose that choice.

This section is intended to make thoroughly clear what is believed to
be a consequence of the rest of this License.

\item
If the distribution and/or use of the Program is restricted in
certain countries either by patents or by copyrighted interfaces, the
original copyright holder who places the Program under this License
may add an explicit geographical distribution limitation excluding
those countries, so that distribution is permitted only in or among
countries not thus excluded.  In such case, this License incorporates
the limitation as if written in the body of this License.

\item
The Free Software Foundation may publish revised and/or new versions
of the General Public License from time to time.  Such new versions will
be similar in spirit to the present version, but may differ in detail to
address new problems or concerns.

Each version is given a distinguishing version number.  If the Program
specifies a version number of this License which applies to it and ``any
later version'', you have the option of following the terms and conditions
either of that version or of any later version published by the Free
Software Foundation.  If the Program does not specify a version number of
this License, you may choose any version ever published by the Free Software
Foundation.

\item
If you wish to incorporate parts of the Program into other free
programs whose distribution conditions are different, write to the author
to ask for permission.  For software which is copyrighted by the Free
Software Foundation, write to the Free Software Foundation; we sometimes
make exceptions for this.  Our decision will be guided by the two goals
of preserving the free status of all derivatives of our free software and
of promoting the sharing and reuse of software generally.

\begin{center}
{\Large\sc
No Warranty
}
\end{center}

\item
{\sc Because the program is licensed free of charge, there is no warranty
for the program, to the extent permitted by applicable law.  Except when
otherwise stated in writing the copyright holders and/or other parties
provide the program ``as is'' without warranty of any kind, either expressed
or implied, including, but not limited to, the implied warranties of
merchantability and fitness for a particular purpose.  The entire risk as
to the quality and performance of the program is with you.  Should the
program prove defective, you assume the cost of all necessary servicing,
repair or correction.}

\item
{\sc In no event unless required by applicable law or agreed to in writing
will any copyright holder, or any other party who may modify and/or
redistribute the program as permitted above, be liable to you for damages,
including any general, special, incidental or consequential damages arising
out of the use or inability to use the program (including but not limited
to loss of data or data being rendered inaccurate or losses sustained by
you or third parties or a failure of the program to operate with any other
programs), even if such holder or other party has been advised of the
possibility of such damages.}

\end{enumerate}


\begin{center}
{\Large\sc End of Terms and Conditions}
\end{center}


\pagebreak[2]

\section*{Appendix: How to Apply These Terms to Your New Programs}

If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these
terms.

  To do so, attach the following notices to the program.  It is safest to
  attach them to the start of each source file to most effectively convey
  the exclusion of warranty; and each file should have at least the
  ``copyright'' line and a pointer to where the full notice is found.

\begin{quote}
one line to give the program's name and a brief idea of what it does. \\
Copyright (C) yyyy  name of author \\

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
\end{quote}

Also add information on how to contact you by electronic and paper mail.

If the program is interactive, make it output a short notice like this
when it starts in an interactive mode:

\begin{quote}
Gnomovision version 69, Copyright (C) yyyy  name of author \\
Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'. \\
This is free software, and you are welcome to redistribute it
under certain conditions; type `show c' for details.
\end{quote}


The hypothetical commands {\tt show w} and {\tt show c} should show the
appropriate parts of the General Public License.  Of course, the commands
you use may be called something other than {\tt show w} and {\tt show c};
they could even be mouse-clicks or menu items---whatever suits your
program.

You should also get your employer (if you work as a programmer) or your
school, if any, to sign a ``copyright disclaimer'' for the program, if
necessary.  Here is a sample; alter the names:

\begin{quote}
Yoyodyne, Inc., hereby disclaims all copyright interest in the program \\
`Gnomovision' (which makes passes at compilers) written by James Hacker. \\

signature of Ty Coon, 1 April 1989 \\
Ty Coon, President of Vice
\end{quote}


This General Public License does not permit incorporating your program
into proprietary programs.  If your program is a subroutine library, you
may consider it more useful to permit linking proprietary applications
with the library.  If this is what you want to do, use the GNU Library
General Public License instead of this License.

\end{document}

% LocalWords:  proprietarize redistributors sublicense yyyy Gnomovision EULAs
% LocalWords:  Yoyodyne FrontPage improvers Berne copyrightable Stallman's GPLs
% LocalWords:  Lessig Lessig's UCITA pre PDAs CDs reshifts GPL's Gentoo
% LocalWords:  TrollTech