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%   * I have started using  \hyperref[LABEL]{text} extensively, which seems

%     to work great in the PDF and HTML versions, but in the Postscript

%     version, the link lost entirely.  I think we need an additional command

%     to replace \hyperref which takes an optional third argument that will

%     insert additional text only when generating print versions, such as:

%      \newhyperref[GPLv2s3]{the requirements for binary distribution under

%      GPLv2}{(see section~\ref*{GPLv2s3} for more information)}

%

%     This is a careful balance, because it'd be all too easy to over-pepper

%     the printed version with back/forward references, but there are

%     probably times when this is useful.

%   * Similar issue: \href{} is well known not to carry the URLs in the print

%     versions.  Adding a footnote with the URL for the print version is

%     probably right.  (or maybe a References page?)

%   * The text is extremely inconsistent regarding formatting of code and

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%         + \texttt{}

%         + the lstlisting environment (i.e., \begin{lstlisting}

%     These should be made consistent, using only two forms: one for line and

%     one for a long quoted section.

% FIXME: s/GPL enforcers/COGEOs/g

%        (the term coined later but not used throughout) This can't be done

%        by rote, since it may not be appropriate everywhere and shouldn't be

%        used *before* it's coined in the early portions of

%        compliance-guide.tex (and it's probably difficult to coin it earlier

%        anyway).  BTW, I admit COGEOs isn't the best acronym, but I started

%        with ``Community Enforcement Organizations'', which makes CEO, which

%        is worse. :)  My other opting was   COEO, which seemed too close to

%        CEO.  Suggestions welcome.

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\hypersetup{pdfinfo={Title={Copyleft and the GNU General Public License: A Comprehensive Tutorial and Guide}}}

    \begin{document}

\pagestyle{plain}

\pagenumbering{roman}

\frontmatter

\begin{titlepage}

\begin{center}

{\Huge

{\sc Copyleft and the  \\

GNU General Public License:

\vspace{.25in}

A Comprehensive Tutorial \\

\vspace{.1in}

and Guide

}}

\vfill

{\parindent 0in

\begin{tabbing}

Copyright \> \copyright{} 2014--2015 \>  Anthony K. Sebro, Jr. \\

Copyright \= \copyright{} 2014 \> Denver Gingerich. \\

Copyright \= \copyright{} 2003--2007, 2014 \>  Free Software Foundation, Inc. \\

Copyright \> \copyright{} 2008, 2014 \>  Software Freedom Law Center. \\

\end{tabbing}

\vspace{.3in}

The copyright holders grant the freedom to copy, modify, convey,

adapt, and/or redistribute this work (except

Appendices~\ref{GPLv2-full-text}--\ref{AGPLv3-full-text}) under the terms of the Creative Commons

Attribution Share Alike 4.0 International License.  A copy of that license is

available at \url{https://creativecommons.org/licenses/by-sa/4.0/legalcode}.

Appendices~\ref{GPLv2-full-text}--\ref{AGPLv3-full-text} include copies of the texts of various licenses published

by the FSF, and they are all licensed under the license, ``Everyone is permitted

to copy and distribute verbatim copies of this license document, but changing

it is not allowed.''.  However, those who seek to make modified versions of

those licenses should note the

\href{https://www.gnu.org/licenses/gpl-faq.html#ModifyGPL}{explanation given in the GPL FAQ}.

\vfill

As a public, collaborative project, this Guide is primarily composed of the

many contributions received via its

\href{https://k.copyleft.org/guide/files/master/CONTRIBUTING.md}{public

  contribution process}.  Please

\href{https://k.copyleft.org/guide/changelog/master/}{review its

  Git logs} for full documentation of all contributions, and

Appendix~\ref{third-party-citation-list}

  contains a list of third-party works from which some material herein was

adapted.

The most recent version is

available online at \url{https://copyleft.org/guide/}.  Patches

are indeed welcome to this material.  Sources can be found in the Git

repository at \url{https://k.copyleft.org/guide/}.

}

\end{center}

\end{titlepage}

\tableofcontents

\chapter{Preface}

This tutorial is the culmination of nearly a decade of studying and writing

about software freedom licensing and the GPL\@.  Each part of this tutorial

is a course unto itself, educating the reader on a myriad of topics from the

deep details of the GPLv2 and GPLv3, common business models in the copyleft

licensing area (both the friendly and unfriendly kind), best practices for

compliance with the GPL, for engineers, managers, and lawyers, as well as

real-world case studies of GPL enforcement matters.

It is unlikely that all the information herein is necessary to learn all at

once, and therefore this tutorial likely serves best as a reference book.

The material herein has been used as the basis for numerous live tutorials

and discussion groups since 2002, and the materials have been periodically

updated.   They likely stand on their own as excellent reference material.

However, if you are reading these course materials without attending a live

tutorial session, please note that this material is merely a summary of the

highlights of the various CLE and other tutorial courses based on this

material.  Please be aware that during the actual courses, class discussion

and presentation supplements this printed curriculum.  Simply reading this

material is \textbf{not equivalent} to attending a course.

\mainmatter

% FIXME: We need an Introduction.  I think ideally it goes here, before Part

%  I.  The introduction should cover initially:

%

%

%     * Why we cover the topics in the order that we do, in particular, why

%       we discuss all GPLv2 before mentioning  GPLv3 (i.e., explain why we

%       take a diachronic approach to study of GPL).

%

%     * It should briefly discuss Free Culture / Software Freedom stuff.

%       Maybe some early material currently living in gpl-lgpl.tex should move

%       to the introduction, maybe not.  The goal is to prepare for the

%       moment when we can merge in material about CC-BY-SA.

\input{gpl-lgpl}

\input{compliance-guide}

\input{enforcement-case-studies}

\appendix

\part{Appendices}

\input{third-party-citations}

\input{license-texts}

\end{document}

the copyrightable similar features of the works, the court then decides

whether those features are entitled to ``broad'' or ``thin''

protection. ``Thin'' protection is given to non-copyrightable facts or

ideas that are combined in a way that affords copyright protection only

from their alignment and presentation, while ``broad'' protection is given

to copyrightable expression itself. Depending on the degree of protection

afforded, the court then sets the appropriate standard for a subjective

comparison of the works to determine whether, as a whole, they are

sufficiently similar to support a finding that one is a derivative work of

the other. ``Thin'' protection requires the second work be virtually

identical in order to be held a derivative work of an original, while

``broad'' protection requires only a ``substantial similarity.''

\section{No Protection for ``Methods of Operation''}

The First Circuit has taken the position that the AFC test is inapplicable 

when the works in question relate to unprotectable elements set forth in 

\S~102(b).  Their approach results in a much narrower definition

of derivative work for software in comparison to other circuits. Specifically, 

the

First Circuit holds that ``method of operation,'' as used in \S~102(b) of

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).  In Lotus, the court held that a menu command

hierarchy for a computer program was uncopyrightable because it did not

merely explain and present the program's functional capabilities to the

user, but also served as a method by which the program was operated and

controlled. As a result, under the First Circuit's test, literal copying

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.  As a result, courts in the First Circuit that apply the AFC test

do so only after applying a broad interpretation of \S~102(b) to filter out

unprotected elements. E.g., Real View, LLC v. 20-20 Technologies, Inc., 

683 F. Supp.2d 147, 154 (D. Mass. 2010).

\section{No Test Yet Adopted}

Several circuits, most notably the Fourth and Seventh, have yet to

declare their definition of derivative work and whether or not the

AFC, Analytic Dissection, or some other test best fits their

interpretation of copyright law. Therefore, uncertainty exists with

respect to determining the extent to which a software program is a

derivative work of another in those circuits. However, one may presume

that they would give deference to the AFC test since it is by far the

majority rule among those circuits that have a standard for defining

a software derivative work.

\section{Cases Applying Software Derivative Work Analysis}

In the preeminent case regarding the definition of a derivative work for

software, Computer Associates v. Altai, the plaintiff alleged that its

program, Adapter, which was used to handle the differences in operating

system calls and services, was infringed by the defendant's competitive

program, Oscar. About 30\% of Oscar was literally the same code as

that in Adapter. After the suit began, the defendant rewrote those

portions of Oscar that contained Adapter code in order to produce a new

version of Oscar that was functionally competitive with Adapter, without

having any literal copies of its code. Feeling slighted still, the

plaintiff alleged that even the second version of Oscar, despite having no

literally copied code, also infringed its copyrights. In addressing that

question, the Second Circuit promulgated the AFC test.

In abstracting the various levels of the program, the court noted a

similarity between the two programs' parameter lists and macros. However,

following the filtration step of the AFC test, only a handful of the lists

and macros were protectable under copyright law because they were either

in the public domain or required by functional demands on the

program. With respect to the handful of parameter lists and macros that

did qualify for copyright protection, after performing the comparison step

of the AFC test, it was reasonable for the district court to conclude that

they did not warrant a finding of infringement given their relatively minor

contribution to the program as a whole. Likewise, the similarity between

the organizational charts of the two programs was not substantial enough

to support a finding of infringement because they were too simple and

obvious to contain any original expression.

In the case of Oracle America v. Google, 872 F. Supp.2d 974 (N.D. Cal. 2012),

the Northern District of California District Court examined the question of 

whether the application program interfaces (APIs) associated with the Java

programming language are entitled to copyright protection.  While the 

court expressly declined to rule whether all APIs are free to use without 

license (872 F. Supp.2d 974 at 1002), the court held that the command 

structure and taxonomy of the APIs were not protectable under copyright law.

Specifically, the court characterized the command structure and taxonomy as

both a ``method of operation'' (using an approach not dissimilar to the 

First Circuit's analysis in Lotus) and a ``functional requirement for 

compatibility'' (using Sega v. Accolade, 977 F.2d 1510 (9th Cir. 1992) and

Sony Computer Ent. v. Connectix, 203 F.3d 596 (9th Cir. 2000) as analogies),

and thus unprotectable subject matter under \S~102(b). 

Perhaps not surprisingly, there have been few other cases involving a highly

detailed software derivative work analysis. Most often, cases involve

clearer basis for decision, including frequent bad faith on the part of

the defendant or over-aggressiveness on the part of the plaintiff.  

\section{How Much Do Derivative Works Matter?}

It is certainly true that GPL intends for any work that is determined a

``derivative work'' under copyright law must be licensed as a whole under

GPL\@, as will be discussed in the following chapter.  However, as we finish

up our discussion derivative works, we must note that preparation of a

derivative work is by far not the only way to create a new work covered by

GPL\@.

In fact, while derivative work preparation is perhaps the most exciting area

of legal issues to consider, the more mundane ways to create a new work

covered by GPL are much more common.  For example, copyright statutes

generally require permission from the copyright holder to grant explicit

permission to modify a work in any manner.  As discussed in the next chapter,

the GPL {\em does} grant such permission, but requires the modified work must

also be licensed under the terms of the GPL (and only GPL:

see\S~\ref{GPLv2s6} in this tutorial).  Determining whether software was

modified is a substantially easier analysis than the derivative work

discussions and considerations in this chapter.

The question of derivative works, when and how they are made, is undoubtedly

an essential discussion in the interpretation and consideration of copyleft.

That is why this chapter was included in this tutorial.  However, as we

return from this digression and resume discussion of the detailed text of the

GPLv2, we must gain a sense of perspective: most GPL questions center around

questions of modification and distribution, not preparation of derivative

works.  Derivative work preparation is ultimately a small subset of the types

of modified versions of the software a developer might create, thus, while an

excessive focus on derivative works indulges us in the more exciting areas of

copyleft, we must keep a sense of perspective regarding their relative

importance.

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

\chapter{Modified Source and Binary Distribution}

\label{source-and-binary}

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

software. These sections, GPLv2~\S\S2--3, define the central core rights and

requirements of GPLv2\@.

\section{GPLv2~\S2: Share and Share Alike}

\label{GPLv2s2}

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

freedom upon redistribution.  GPLv2~\S2 is the only place in GPLv2

that governs the modification controls of copyright law.  If users

distribute modified versions a GPLv2'd program, they must follow the terms of GPLv2~\S2 in making

those changes.  Thus, this sections ensures that the body of GPL'd software, as it

continues and develops, remains Free as in freedom.

To achieve that goal, GPLv2~\S2 first sets forth that the rights of

redistribution of modified versions are the same as those for verbatim

copying, as presented in GPLv2~\S1.  Therefore, the details of charging money,

keeping copyright notices intact, and other GPLv2~\S1 provisions are intact

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

\subsection{The Simpler Parts of GPLv2~\S2}

% FIXME: GPLv2~\S2(a) isn't discussed heavily here and more should be

% discussed about it.  There have been developer questions.  One idea I had

% was to write up:

%        http://ebb.org/bkuhn/blog/2011/03/11/linux-red-hat-gpl.html

% as a compliance case study specific to GPLv2 Section 2(a)

%

% Another point to discuss here -- or maybe it goes better in the compliance

% case study ? -- is to explain that git logs ARE adequate but possibly

% overkill.

The first (GPLv2~\S2(a)) requires that modified files carry ``prominent

notices'' explaining what changes were made and the date of such

changes. This section does not prescribe some specific way of

marking changes nor does it control the process of how changes are made.

Primarily, GPLv2~\S2(a) seeks to ensure that those receiving modified

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

make proper support choices.  Finally, GPLv2~\S2(a) serves an academic

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

approach to understand the software.

GPLv2~\S2(c), a relatively simple section, requires that any program which

(before modification) ``normally reads commands interactively when run'' and

displays or prints legal information also display all copyright notices,

warranty disclaimer, modification indications and a pointer to the license,

even in modified versions.  The requirement is relatively simple, and relates

to an important policy goal of copyleft: downstream users should be informed

of their rights.  Its implications and details are straightforward and

simple.

\subsection{GPLv2~\S2(b)}

Meanwhile, GPLv2~\S2(b) requires careful and extensive study.  Its four short lines embody

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

considered by some to be the most worthy of careful scrutiny because they

can be a source of great confusion when not properly understood.

In considering GPLv2~\S2(b), first note the qualifier: it \textit{only} applies to

derivative, combined and/or modified works that ``you distribute or publish''.  Despite years of

education efforts on this matter, many still believe that modifiers

of GPL'd software \textit{must} publish or otherwise

share their changes.  On the contrary, GPLv2~\S2(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{Most Free Software enthusiasts believe there is a {\bf

    moral} obligation to redistribute changes that are generally useful,

  and they often encourage 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 GPLv2~\S0, 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 copyright law.

If, under copyright law, the modified version ``contains or is

derived from'' the GPL'd software, then the requirements of GPLv2~\S2(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 GPLv2~\S2(b) describes what the licensee must do if she

distributes or publishes a modified version of the work --- 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 GPLv2~\S2 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 work distributed to

the programmer under GPL\@. Thus, the license of the original work

affects the license of the new whole combined and/or derivative work.

% {\cal I}

\newcommand{\gplusi}{$\mathcal{G\!\!+\!\!I}$}

\newcommand{\worki}{$\mathcal{I}$}

\newcommand{\workg}{$\mathcal{G}$}

\label{separate-and-independent}

It is certainly possible to take an existing independent work (called

\worki{}) and combine it with a GPL'd 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 combined work, \gplusi{}, is held by the original copyright

holder of each of the two works.

In this case, GPLv2~\S2 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 proprietary

product --- would its copyright holders  give you permission to create and distribute

\gplusi{} without paying them a hefty sum?)  The license of \workg{}, the

GPL, states the  options for the copyright holder of \worki{}

who may want to create and distribute \gplusi{}. The  GPL's pre-granted

permission to create and distribute combined and/or derivative works, provided the terms

of the 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 condition is any way unreasonable is simply ludicrous.

The GPL  recognizes what is outside its scope.  When a programmer's work is

``separate and independent'' from any GPL'd program code with which it could be

combined, then the obligations of copyleft do not extend to the work

separately distributed.  Thus, Far from attempting to extend copyleft beyond the

scope of copyright, the licenses explicitly recognize.

Thus, GPL recognizes what is outside its scope.  When a programmer's work is

``separate and independent'' from any GPL'd program code with which it could

be combined, then copyleft obligations do not extend to the independent work

separately distributed.  Thus, far from attempting to extend copyleft beyond

the scope of copyright, GPL explicitly limits the scope of copyleft to the

scope of copyright.

GPL does not, however (as is sometimes suggested) distinguish ``dynamic''

from ``static'' linking of program code.  It is occasionally suggested that a

subroutine ``dynamically'' linked to GPL'd code is, by virtue of the linking

alone, inherently outside the scope of copyleft on the main work.  This is a

misunderstanding.  When two software components are joined together to make

one work (whether a main and some library subroutines, two objects with their

respective methods, or a program and a ``plugin'') the combination infringes

the copyright on the components if the combination required copyright

permission from the component copyright holders, as such permission was

either not available or was available on terms that were not observed.

In other words, when combining other software with GPL'd components, the only

available permission is GPL\@.  The combiner must observe and respect the GPL

observed on the combination as a whole.  It matters not if that combination

is made with a linker before distribution of the executable, is made by the

operating system in order to share libraries for execution efficiency at

runtime, or results from runtime references in the language at runtime (as in

Java programs).

% FIXME-SOON:

%   A commonly asked question is whether or not separated distribution (i.e.,

%   dynamic loading of a module that is expected to be present on the

%   downstream sytem) triggers the copyleft requirement.  The text above

%   hints at that issue, with reference to Java runtime.  However, here would

%   likely be the natural place to discuss that issue in more depth.  I have

%   never actually studied this specific question in a GPLv2 vs. GPLv3

%   analysis, and as such I'd want to do that first.  Furthermore, the FSF

%   has not publicly opined on this question to my knowledge, so I'd want to

%   see possible update to

%   http://www.gnu.org/licenses/gpl-faq.html#GPLStaticVsDynamic to mention

%   this issue before opining about it in the Guide.

%   I'm not aware, BTW, of any dissenting opinions or disagreements among

%   copyleft advocates on this point.  I think it's just a question that is

%   rarely opined on but often asked, so it's fitting for this Guide to cover

%   it, and for addition on this point in the FAQ.

\medskip

\label{GPLv2s2-at-no-charge}

The next phrase of note in GPLv2~\S2(b) is ``licensed \ldots at no charge.''

This phrase  confuses many.  The sloppy reader points out this as ``a

contradiction in GPL'' because (in their confused view) that clause of GPLv2~\S2 says that re-distributors cannot

charge for modified versions of GPL'd software, but GPLv2~\S1 says that

they can.  Avoid this confusion: the ``at no charge'' \textbf{does not} prohibit re-distributors from

charging when 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'd 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.

GPLv2~\S2(b) further states that the software must ``be licensed \ldots to all

third parties.''  This too yields some confusion, and feeds the

misconception mentioned earlier --- that all modified versions must be 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 GPLv2~\S2(b) does require re-distributors to license the whole work in

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

copy of the software.

In summary, GPLv2\ 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 GPLv2.  When an entity \emph{chooses} to redistribute

a work based on GPL'd software, the license of that whole 

work must be GPL and only GPL\@.  In this manner, GPLv2~\S2(b) dovetails nicely

with GPLv2~\S6 (as discussed in Section~\ref{GPLv2s6} of this tutorial).

\medskip

The final paragraph of GPLv2~\S2 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'd

code-base does not impact the license of other programs.  A programmer must

expend actual effort  to cause a work to fall under the terms

of the GPL.  Redistributors are always welcome to simply ship GPL'd

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'd.

%FIXME: need discussion of GPLv2's system library exception somewhere in here.

\subsection{Right to Private Modification} 

\label{gplv2-private-modification}

The issue of private modifications of GPLv2'd works deserves special

attention.  While these rights are clearly explicit in GPLv3~\S2\P2 (see

\S~\ref{GPLv3S2} of this tutorial for details), the permission to create

private modifications is mostly implicit in GPLv2.  Most notably, the

requirements of GPLv2~\S2 (and GPLv2~\S3, which will be discussed next) are

centered around two different copyright controls: both modification

\emph{and} distribution.  As such, GPLv2~\S2's requirements need only be met

when a modified version is distributed; one need not follow them for modified

versions that are not distributed.\footnote{As a matter of best practice, it's

  useful to assume that all software may eventually be distributed later,

  even if there no plans for distribution at this time.  Too often, GPL

  violations occur because of a late distribution decision of software that

  was otherwise never intended for distribution.}

However, the careful reader of GPLv2 will notice that, unlike GPLv3, no other

clauses of the license actually give explicit permission to make private

modifications.  Since modification of software is a control governed by

copyright, a modifier needs permission from the copyright holder to engage in

that activity.

In practice, however, traditional GPLv2 interpretation has always assumed

that blanket permission to create non-distributed modified versions was

available, and the

\href{http://www.gnu.org/licenses/gpl-faq.html#GPLRequireSourcePostedPublic}{FSF

  has long opined that distribution of modified versions is never mandatory}.

This issue is one of many where GPLv3 clarifies in explicit text the implicit

policy and intent that was solidified via long-standing interpretation of

GPLv2.

\section{GPLv2~\S3: Producing Binaries}

\label{GPLv2s3}

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, even one written by

William Faulkner, must be 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

modified versions (and/or derivative works) of the source code.  Applying a systematic process (i.e.,

``compilation''\footnote{``Compilation'' in this context refers to the

  automated computing process of converting source code into binaries.  It

  has absolutely nothing to do with the term ``compilation'' in copyright statues.}) 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'd software to be useful, the GPL, since it governs the

rules for creation of modified 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 modified works of the software's

source code.  GPLv2~\S3 addresses the matter of creation and distribution of

binary versions.

Under GPLv2~\S3, binary versions may be created and distributed under the

terms of GPLv2~\S1--2, so all the material previously discussed applies

here.  However, GPLv2~\S3 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.  GPLv2~\S3 must ensure that the binaries are never

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

through the distribution chain.

GPLv2~\S3 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 GPLv2~\S3(a).

\label{GPLv2s3a}

GPLv2~\S3(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).

\subsection{Complete, Corresponding Source (CCS)}

Under GPLv2~\S3(a), the source 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''.   GPLv2~\S3's penultimate paragraph

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 chooses, 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.

Based on the appearance of those two words, GPL theorists will often refer to

the source code required under the previsions of this section as ``Complete,

Corresponding Source'', sometimes abbreviated as CCS\@.  CCS is not a formal,

defined term in GPLv2, but rather, GPL theorists coined the acronym CCS to

embody not just the concepts of ``complete'' and ``corresponding'' as found

in GPLv2, but the entirety of GPLv2's requirements for source code

provisioning.  In other words, GPL theorists might say: ``the company

provided some source, but it wasn't CCS'', which would mean the source code

failed in some ways to meet some term of GPLv2.

\label{GPLv2s3-build-scripts}

Indeed, CCS needs completely include not just that source which is directly

translated by the compiler into object code, but other materials necessary to

convert the source into equivalent binaries.  Specifically, GPLv2~\S3

requires 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 modified works from the sources provided.

This requirement is not merely of theoretical value.  If you pay a high price

for a copy of GPL'd binaries (which comes with CCS, of course), you have the

freedom to redistribute that work at any fee you choose, or not at all.

Sometimes, companies attempt a GPL-violating cozenage whereby they produce

very specialized binaries (perhaps for 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.  Such distributions violate GPL, since the downstream users cannot

effectively ``control compilation and installation'' of the binaries.

\subsection{Additional Source Provision Options}

Software distribution comes in many

forms.  Embedded manufacturers, for example, have the freedom to put

GPL'd software into mobile devices 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 unfeasible.

\label{GPLv2s3-medium-customarily}

GPLv2~\S3, therefore, allows source code to be provided on any physical

``medium customarily used for software interchange.''  By design, this

phrase covers a broad spectrum --- the phrase seeks to pre-adapt to

changes in  technology.  When GPLv2 was first published in June

1991, distribution on magnetic tape was still common, and CD was

relatively new.  By 2002, CD was the default.  By 2007, DVD's were the

default.  Now, it's common to give software on USB drives and SD cards.  This

language in the license 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 in industrialized countries, it is indeed customary to

simply download a CDs' worth of data quickly.  However, even today in the USA, many computer users are not connected to the Internet, and most people connected

to the Internet still have limited download speeds.  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 are normalized for a worldwide userbase.  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 GPLv2~\S3. \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 GPLv2~\S3.

\medskip

As is shown above, under GPLv2~\S3(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'd software. For this situation and others like it, GPLv2\S~3(b) is available.

\label{GPLv2s3b}

GPLv2~\S3(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 GPLv2~\S3(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, GPLv2~\S3(b) does place lasting long-term obligations on 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

would have had to do under GPLv2~\S3(a)) at a moment's notice when 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

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 GPLv2~\S\S1--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.

GPLv2~\S3(c) is created to save her some trouble, because by itself GPLv2~\S3(b)

would unfairly favor large companies.  GPLv2~\S3(b) allows the

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 re-distributors, 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, GPLv2~\S3(b)'s compromise primarily benefits companies that

distribute binary software commercially.  Without GPLv2~\S3(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 GPLv2~\S3(b)-compliant

offer, would be required under GPLv2 (sans GPLv2~\S3(c)) to acquire the source,

merely to give a copy of the software to a friend who needed it.  GPLv2~\S3(c)

reshifts this burden to entity who benefits from GPLv2~\S3(b).

GPLv2~\S3(c) allows those who undertake \emph{noncommercial} distribution to

simply pass along a GPLv2~\S3(b)-compliant source code offer.  The customer who

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,

she would have to acquire the source and either comply via GPLv2~\S3(a), or

write her own GPLv2~\S3(b)-compliant source offer.

This process is precisely the reason why a GPLv2~\S3(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 noncommercially receiving a copy of the

software.  Companies who choose to comply via GPLv2~\S3(b) must thus be

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

many other additional necessary complications under GPLv2~\S\S3(b--c), it is

only rarely a better option than complying via GPLv2~\S3(a).

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

\chapter{GPL's Implied Patent Grant}

\label{gpl-implied-patent-grant}

We digress again briefly from our section-by-section consideration of GPLv2

to consider the interaction between the terms of GPL and patent law. The

GPLv2, despite being silent with respect to patents, actually confers on its

licensees more rights to a licensor's patents than those licenses that

purport to address the issue. This is the case because patent law, under

the doctrine of implied license, gives to each distributee of a patented

article a license from the distributor to practice any patent claims owned

or held by the distributor that cover the distributed article. The

implied license also extends to any patent claims owned or held by the

distributor that cover ``reasonably contemplated uses'' of the patented

article. To quote the Federal Circuit Court of Appeals, the highest court

for patent cases other than the Supreme Court:

\begin{quotation}

Generally, when a seller sells a product without restriction, it in

effect promises the purchaser that in exchange for the price paid, it will

not interfere with the purchaser's full enjoyment of the product

purchased. The buyer has an implied license under any patents of the

seller that dominate the product or any uses of the product to which the

parties might reasonably contemplate the product will be put.

\end{quotation}

Hewlett-Packard Co. v. Repeat-O-Type Stencil Mfg. Corp., Inc., 123 F.3d

1445, 1451 (Fed. Cir. 1997).

Of course, Free Software is licensed, not sold, and there are indeed

restrictions placed on the licensee, but those differences are not likely

to prevent the application of the implied license doctrine to Free

Software, because software licensed under the GPL grants the licensee the

right to make, use, and sell the software, each of which are exclusive

rights of a patent holder. Therefore, although the GPLv2 does not expressly

grant the licensee the right to do those things under any patents the

licensor may have that cover the software or its reasonably contemplated

uses, by licensing the software under the GPLv2, the distributor impliedly

licenses those patents to the GPLv2 licensee with respect to the GPLv2'd

software.

An interesting issue regarding this implied patent license of GPLv2'd