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

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.

  \item The differences between GPLv2 and GPLv3.

  \item The obligations when modifying GPLv2'd or GPLv3'd software.

  \item How existing GPL'd software can be used in existing enterprises.

  \item The basics of LGPLv2.1 and LGPLv3, and how they

  \item The basics to begin understanding the complexities regarding

    derivative and combined works of software.

In January 1989, the FSF announced that the GPL had been converted into a

``subroutine'' that could be reused not just for all FSF-copyrighted

programs, but also by anyone else.  As the FSF claimed in its announcement of

  \href{http://www.gnu.org/bulletins/bull6.html\#SEC8}{GNU's Bulletin, vol 1,

    number 6 dated January 1989}.  (Thanks very much to Andy Tai for his

  \href{http://www.free-soft.org/gpl_history/}{consolidation of research on

\medskip

to run specifically by stating the following:

\begin{quote}

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

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

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

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

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).

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

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

licensor may have that cover the software or its reasonably contemplated

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

software.

This theory comports well with the idea of Free Software, whereby software

is distributed among many entities within the community for the purpose

of constant evolution and improvement. In this way, the law of implied

benefits from the licensing of patents to any single community member.

Note that simply because GPLv2'd software has an implied patent license does

 \renewcommand{\theenumi}{\alph{enumi}}

 \renewcommand{\labelenumi}{\textup{(\theenumi)}}

  holder, and

with respect to the licensed software.

\end{enumerate}

\newcommand{\compA}{$\mathcal{A}$}

For example, if Company \compA{} has a patent on advanced Web browsing, but

cannot assert the patent against any party based on that party's use of 

Company \compA{}'s GPL'd Web browsing software program, or on that party's

creation and use of modified versions of that GPL'd program.  However, if a

party uses that program without

infringement claims against the non-GPLv2-compliant party and

infringement of the patent, because the implied patent license only

Company \compB{} distributes a competitive advanced Web browsing program 

that is not a modified version of Company \compA{}'s GPL'd Web browsing software

program, Company \compA{} is free to assert its patent against any user or

distributor of that product. It is irrelevant whether Company \compB's

implied licenses to Company \compA's patent.

This result also reassures companies that they need not fear losing their

proprietary value in patents to competitors through the GPLv2 implied patent

terms can benefit from the implied patent license. To continue the

example above, Company \compB{} does not receive a free ride on Company

\compA's patent, as Company \compB{} has not licensed-in and then

\compB{} does do that, however, Company \compA{} still has not lost

competitive advantage against Company \compB{}, as Company \compB{} must then,

when it re-distributes Company \compA's program, grant an implied license

to any of its patents that cover the program. Further, if Company \compB{}

relicenses an improved version of Company A's program, it must do so under

are impliedly licensed to any licensee. As such, the only way Company

\compB{} can benefit from Company \compA's implied patent license, is if it,

itself, distributes Company \compA's software program and grants an

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

core freedom-defending provisions of GPLv2\@, which are in GPLv2~\S\S0--3.

not infringed, are enforceable, are kept to the confines of copyright law but

also not trumped by other copyright agreements or components of other

entirely separate legal systems.  In short, while GPLv2~\S\S0--3 are the parts

new licensee.  Under GPLv2~\S6, 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

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

The second sentence of GPLv2~\S6 does the opposite; it bounds from the top.  It

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

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

liability.

\section{GPLv2~\S9: FSF as Stewards of GPL}

with GPLv2 and who did not participate in the GPLv3 process.

Those who wish to drink from the firehose and take a diachronic approach to

occurred from Monday 16 January 2006 through Monday 19 November 2007) should

visit \url{http://gplv3.fsf.org/}.

of the wording in GPLv3 to be simpler and clearer than its GPLv2

counterparts.

defines two terms that are otherwise exotic to the language of international

copyright.

public'' or ``communication to the public'' as one of the exclusive rights of

copyright holders.

that require permission under ``applicable copyright law'', but excludes

execution and private modification from the definition.  GPLv3's definition

also gives examples of activities that may be included within ``propagation''

requirements.  Specifically, GPLv3~\S2\P2 guarantees the basic freedoms of

privately modifying and running the program.  While these basic freedoms were

generally considered a standard part of users' rights under GPLv2 as well,

direct analog to the first sentence of GPLv3~\S2\P2 in GPLv2

(See \S~\ref{gplv2-private-modification} of this tutorial for more on this issue.)

\label{GPLv3s4}

GPLv3~\S4 is a revision of GPLv2~\S1 (as discussed in \S~\ref{GPLv2s1} of

GPLv2~\S1, other than to use the new defined terms.

The only notable change, of ``a fee'' to ``any price or no price'', is in the

removes the term ``physical.''

GPLv3~\S4 has also been revised from its corresponding section in GPLv2 in

Specifically, a distributor of verbatim copies of the program's source code

must obey any existing additional terms that apply to parts of the program

pursuant to GPLv3~\S7.  In addition, the distributor is required to keep

party; rather, only those ``who possess the object code'' can exercise

the offer.  (Note that this is a substantial narrowing of requirements of

offer fulfillment, and is a wonderful counterexample to dispute claims that

% FIXME:  probably mostly still right, needs some updates, though.

additional terms.  With its carefully limited list of allowed additional

requirements, GPLv3\S7 accomplishes additional objectives as well, since it

permits the expansion of the base of code available for GPL developers, while

include by default.

However, any other non-permissive additional terms apart from those stated

Therefore, GPLv3~\S11 introduces the terms ``contributor'', ``contributor version'', and

``essential patent claims'', which are

Program, contributors include all the copyright holders for the Program,

other than copyright holders of material originally licensed under non-GPL

terms and later incorporated into a GPL-covered work.  The contributors are