restrictions make software proprietary.} Copyright law, with respect to

software, typically governs copying, modifying, and redistributing that

software (For details of this in the USA, see

\href{http://www.law.cornell.edu/uscode/text/17}{Title 17} of the

\textit{United States Code}).\footnote{Copyright law in general also governs

  ``public performance'' of copyrighted works. There is no generally agreed

fixed in any tangible medium of expression ...  from which they can be

perceived, reproduced, or otherwise communicated, either directly or with the

aid of a machine or device'' (as stated in

covered by the statues, and is copyrighted by default.

However, software, in its natural state without copyright, is Free

The best example of software known to be in the public domain is software

that is published exclusively produced by the USA government.  Under

works published by the USA Government are not copyrightable.

\subsection{Why Copyright Free Software?}

\begin{itemize}

\item Software patents and their danger are explicitly mentioned, inspiring

  detail in \S~\ref{GPLv2s5}, \S~\ref{GPLv2s6} and \S~\ref{GPLv2s7} of this

  tutorial.)

  \S~\ref{GPLv2s2} in this tutorial).

 ``the scripts used to control compilation and installation of the

  executable'', which is a central component of current GPLv2 enforcement

  \S~\ref{GPLv2s3} in this tutorial).

\end{itemize}

0--2. These are the straightforward sections of the GPL that define the

simplest rights that the user receives.

\label{GPLv2s0}

the work.  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.

system that can restrict the software.  Specifically, it states:

\begin{quote}

Activities other than copying, distribution and modification are not

\begin{quote}

''The act of running the Program is not restricted.''

\end{quote}

\medskip

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

even the GNU GPL --- can be blamed for this.  Legislators and court

opinions must give us guidance to decide the border cases.

\label{GPLv2s1}

exactly as it was received. This section is quite straightforward.

However, there are a few details worth noting here.

freedom to publish a book that is the printed copy of the program's source

vendors may ship Free Software on a CD, but others may place it right on

is allowed.

Preservation of copyright notice and license notifications are mentioned

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

Sections~\ref{GPLv2s11} and~\ref{GPLv2s12} of this tutorial for more on GPL's

warranty disclaimers.)

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

We digress for this chapter from our discussion of GPL's exact text to

consider the matter of derivative works --- a concept that we must

Software licensing in general, relies critically on the concept of

``derivative work'' since software that is ``independent,'' (i.e., not

``derivative'') of Free Software need not abide by the terms of the

`work based on the Program' means either the Program or any derivative

work under copyright law.'' It is being a derivative work of Free Software

that triggers the necessity to comply with the terms of the Free Software

These are the only provisions in the Copyright Act relevant to the

determination of what constitutes a derivative work of a computer

program. Another provision of the Copyright Act that is also relevant to

\begin{quotation}

In no case does copyright protection for an original work of authorship

myriad of rules and procedures to sift from a program all the portions

that are not eligible for copyright protection.

embodied in the program are to be denied copyright protection. However,

implementing this rule is not as easy as it first appears. The courts

readily recognize the intrinsic difficulty in distinguishing between ideas

The First Circuit expressly rejected the AFC test and, instead, takes a

much narrower view of the meaning of derivative work for software. The

the Copyright Act, refers to the means by which users operate

computers. Lotus Development Corp. v. Borland Int’l., Inc., 49 F.3d 807

(1st Cir. 1995). More specifically, the court held that a menu command

of a menu command hierarchy, or any other ``method of operation,'' cannot

form the basis for a determination that one work is a derivative of

another. It is also reasonable to expect that the First Circuit will read

promulgate a definition of derivative work that is much narrower than that

which exists under the AFC test.

In this chapter, we discuss the two core sections that define the rights

and obligations for those who modify, improve, and/or redistribute GPL'd

requirements of GPLv2\@.

For many, this is where the ``magic'' happens that defends software

that governs the modification controls of copyright law. If someone

continues and develops, remains Free as in freedom.

redistribution of modified versions are the same as those for verbatim

here as well. However, there are three additional requirements.

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 nor controlling the process of how changes get made.

versions know the history of changes to the software. 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 about the

historical context of the software version they use, so that they can

purpose --- ensuring that future developers can use a diachronic

approach to understand the software.

\medskip

the legal details of ``share and share alike.''  These 46 words are

derivative works that ``you distribute or publish.''  Despite years of

education efforts by FSF on this matter, many still believe that modifiers

of GPL'd software are required by the license to publish or otherwise

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

  is a clear distinction between what one {\bf ought} to do and what one

  {\bf must} do.}

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

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.

distributing or publishing a work that is deemed a derivative work under

copyright law --- namely, the following:

\begin{quote}

Consider each subpart carefully.

The work ``as a whole'' is what is to be licensed. This is an important

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

this combined work, \gplusi{}, is held by the original copyright

holder of each of the two works.

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

\medskip

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

they can. The ``at no charge'' does not prohibit redistributors from

charging when performing the acts governed by copyright

law,\footnote{Recall that you could by default charge for any acts not

the copy to the customer, but they may not charge a separate licensing

fee for the software.

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,

a way that extends to all third parties who may ultimately receive a

copy of the software.

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'd software, the license of that whole derivative

\medskip

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

as long as the terms of GPL are adhered to for those packages that are

truly GPL'd.

\label{GPL-Section-3}

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

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

binary versions.

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

distributed without the source code, so that these freedoms are passed

through the distribution chain.

distribution of source code along with binaries. The most common and the

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).

code.''  Here ``corresponding'' primarily means that the source code

provided must be that code used to produce the binaries being distributed.

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

complete source, it would not be possible to make changes that were

actually directly derived from the version received.

seen in FSF's GPL enforcement. Under GPL, if you pay a high price for

a copy of GPL'd binaries (which comes with corresponding source, of

course), you have the freedom to redistribute that work at any fee you

an obscure architecture). They then give source code that does

correspond, but withhold the ``incantations'' and build plans they

used to make that source compile into the specialized binaries.

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

recommended that this be the default way that people comply with GPL, the

GPL does provide options when such distribution is infeasible.

``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

useful thing to do --- is not usually sufficient.

Note, however, a major exception to this rule, given by the last paragraph

Internet (i.e., ``from a designated place''), \emph{then} simply providing

the source code right alongside the binaries in the same place is

\medskip

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'd software. For this situation and others like it, \S

3(b) is available.

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

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

windfalls.

However, note that regardless of how many users prefer to get the

binary distributor. The binary distributor must be prepared to honor

that offer for source for three years and ship it out (just as they

receive such a request. There is real organizational cost here:

support engineers must be trained how to route source requests, and

source CD images for every release version for the last three years

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

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

GPL --- including the freedom to modify, rebuild, and redistribute the

source code.

separation of 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

along the distribution chain must have the right to get the source and

exercise those freedoms that require it.

would be at the detriment of the companies' customers; the burden of

source code provision would be unfairly shifted to the companies'

wishes 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,

valid for all third parties. At the time the offer is made, there is no

way of knowing who might end up noncommercially receiving a copy of the

prepared to honor all incoming source code requests. For this and the

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\chapter{GPL's Implied Patent Grant}

\chapter{Defending Freedom on Many Fronts}

Chapters~\ref{run-and-verbatim} and ~\ref{source-and-binary} presented the

are enforceable, are kept to the confines of copyright law, and are not

trumped by other copyright agreements or components of other entirely

the parts of the license that keep the playing field clear so that \S\S

0--3 can do their jobs.

\label{GPLv2s4}

strange that a license with 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

In fact, when an entity looses their right to copy, modify and distribute

GPL'd software, it is because of their \emph{own actions}, not that of

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

then all rights under the license --- even those otherwise permitted for

those who have not violated --- terminate automatically.

they are stuck. They must completely cease and desist from all

copying, modification and distribution of that GPL'd software.

would ever consider undertaking or even endorsing, it is a legal way for

copyright holders to proceed.

\label{GPLv2s5}

confusion about GPLv2\@. 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

This is a certainly subtle point, and requires a mindset quite different

from the contractual approach taken by EULA authors.

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

\section{Using GPL Both as a Contract and Copyright License}

\label{GPLv2s6}

was the irrevocable nature of the GPL\@. The GPLv2 is indeed irrevocable,

distribution chain, that each licensor can pass along the license to each

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 GPLv2\@. In a mathematical sense, this bounds the bottom ---

making sure that future licensees get no fewer rights than the licensee before.

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 GPLv2\@.

entity in the distribution chain is responsible for the compliance of any

other. This is particularly important for noncommercial users who have

only copyright license allowing you to copy, modify and distribute the

software.

\label{GPLv2s7}

distributor knows of that would prohibit later licensees from exercising

their full rights under GPL, then distribution is prohibited.

those patents. Many companies, including IBM, the largest patent holder

in the world, have chosen the latter.

Instead, it is inspiring patent holders to share their patents in the same

freedom-defending way that they share their copyrighted works.

\label{GPLv2s8}

particular country, say Unfreedonia, grants particular patents or allows

copyrighted interfaces (no country to our knowledge even permits those

yet), that the GPLv2'd software can continue in free and unabated

distribution in the countries where such controls do not exist.

knew of a patent in a particular country licensed in a GPL-incompatible

way, then she could not distribute under GPL, because the work could

legitimately end up in the hands of citizens of Unfreedonia.

It is an inevitable but sad reality that some countries are freer than

free without otherwise negating parts of the license.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

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

of the GPLv2 handles administrivia and issues concerning warranties and

liability.

\label{GPLv2s9}

FSF reserves the exclusive right to publish future versions of the GPL\@;

of GPL'd 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

a gigantic community depends on that freedom now. FSF hopes to take all

stakeholders' opinions under advisement.

\label{GPLv2s10}

copyright law. Namely, the copyright holder of a particular software

program has the prerogative to grant alternative agreements under separate

copyright licenses.

\label{GPLv2s11}

All warranty disclaimer language tends to be shouted in all capital

to be voodoo tradition of warranty disclaimer writing.

Some have argued the GPL is unenforceable in some jurisdictions because

contains a jurisdictional savings provision, which states that it is to be

interpreted only as broadly as allowed by applicable law. Such a

provision ensures that both it, and the entire GPL, is enforceable in any

jurisdiction, regardless of any particular law regarding the

permissibility of certain warranty disclaimers.

\label{GPLv2s12}

There are many types of warranties, and in some jurisdictions some of them

cannot be disclaimed. Therefore, usually agreements will have both a

11 thus gets rid of all implied warranties that can legally be

warranties that cannot legally be disclaimed in a particular jurisdiction.

Again, some have argued the GPL is unenforceable in some jurisdictions

because its limitation of liability is impermissibly broad. However, \S

provision, which states that it is to be interpreted only as broadly as

allowed by applicable law. As stated above, such a provision ensures that

regardless of any particular law regarding the permissibility of limiting

liability.

\section{Understanding GPLv3 As An Upgraded GPLv2}

\label{GPLv3s3}

\section{Understanding License Compatibility}

\label{license-compatibility}

\label{GPLv3s11}

\label{GPlv2s14}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

identical, or that have the minor modification changing the word

``Program'' to ``Library.''

section handles termination in precisely the same manner.

the license is a copyright license, and handle the acceptance of those

copyright terms.

distribution system of Free Software under these licenses, to ensure that

up, down, and throughout the distribution chain, each recipient of the

software receives identical rights under the license and no other

restrictions are imposed.

other claims and legal realities, such as patent licenses and court

judgments, do not trump the rights and permissions granted by these