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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),

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

\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

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

Users must have the right to engage in a non-commercial environment of

finding help with the software (as often happens on email lists and in

users groups).  This means 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.  Each user, or

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}

  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

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.

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?}

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

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

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

canonical version.  Meanwhile, many other individuals have gotten involved

non-commercially as developers, because they want to ``cut their teeth on

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,

    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 defend themselves in court or write their own briefs

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

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

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

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

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

Many consider \S 2 the heart and soul of the GPL\@.  For many, this is

where the ``magic'' happens that defends software freedom along the

where it is.  However, I argue that the heart is in fact contained in \SS

4--5 (see Section~\ref{GPLs4} and~\ref{GPLs5} of this tutorial).  But, for

the moment, let us consider the soul.

\S 2 gives the only permission in the GPL that governs the modification

controls of copyright law.  If someone modifies a GPL'ed program, she is

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 changes to software that are not shared should be protected and

defended\footnote{FSF does maintain that there is an {\bf ethical}

  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:

% 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

human eyes and ears to have any value.

representation of software is of keen interest to programmers, users and

programmers alike cannot make the proper use of software in that

be fully useful.  Without the binaries, be they in object or executable

Under copyright law, binary representations of the software are simply

derivative works of the source code.  Applying a systematic process (i.e.,

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

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

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

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}

\label{GPLs7}

\label{GPLs8}

\section{GPL \S 9}

\label{GPLs9}

\section{GPL \S 10}

\label{GPLs10}