decide whether or not to implicitly trust the FSF in its work of drafting

future GPL versions.  The FSF, for its part, does encourage copyright holders

to chose by default ``GPLv$X$-or-later'' (where $X$ is the most recent

version of the GPL published by the FSF).  However, the FSF \textbf{does not

  mandate} that a choice to use any GPL requires a copyright holder ceding

its authority for future licensing decisions to the FSF.  In fact, the FSF

considered this possibility for GPLv3 and chose not to do so, instead opting

for the third-party steward designation clause discussed in

\section{Complexities of Two Simultaneously Popular Copylefts}

Obviously most GPL advocates would prefer widespread migration to GPLv3, and

many newly formed projects who seek a copyleft license tend to choose a

GPLv3-based license.  However, many existing copylefted projects continue

with GPLv2-only or GPLv2-or-later as their default license.

\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}

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

modifies 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.

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

expended 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.

\section{GPLv2~\S3: Producing Binaries}

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 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.

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)

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

thesis to consider, based on the combined decades of experience in GPL

interpretation of this tutorial's authors: the harder and more strained the

reader must study and read the system library exception, the more likely it

is that the library in question does not qualify for it.

\section{GPLv3~\S2: Basic Permissions}

GPLv3~\S2 can roughly be considered as an equivalent to GPLv2~\S0 (discussed

improvements found in GPLv3 are found here as well.  For example, the first

sentence of GPLv3~\S2 furthers the goal internationalization.  Under the

copyright laws of some countries, it may be necessary for a copyright license

to include an explicit provision setting forth the duration of the rights

being granted. In other countries, including the USA, such a provision is

unnecessary but permissible.

GPLv3~\S2\P1 also acknowledges that licensees under the GPL enjoy rights of

% FIXME: say more and tie it to the text

There is no harm in explicitly pointing out what ought to be obvious: that

those who convey GPL-covered software may offer commercial services for the

support of that software.

\section{GPLv3~\S5: Modified Source}

% FIXME: 5(a) is slightly different in final version

Section 5 contains a number of changes relative to the corresponding section

in GPLv2. Subsection 5a slightly relaxes the requirements regarding notice of

changes to the program. In particular, the modified files themselves need no

longer be marked. This reduces administrative burdens for developers of

modified versions of GPL'd software.

results in a new program based on the old program, with different functional

characteristics created by the merger of two expressions: the original

program and the added parts.  Such added parts are ``by their nature

extensions of'' the old program, and therefore the entire new program which

they and the old program form must be licensed under the GPL.  As subsection

5c states, packaging of a work has no bearing on the scope of copyleft.

\section{GPLv3~\S6: Non-Source and Corresponding Source}

Section 6 of GPLv3, which clarifies and revises GPLv2 section 3, requires

distributors of GPL'd object code to provide access to the corresponding

source code, in one of four specified ways. As noted above, ``object code''

in GPLv3 is defined broadly to mean any non-source version of a work.

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

combination and do not wish to use code under the Affero requirement may

remove the Affero-covered portion of the combination.

Those who criticize the permission to link with code under the Affero

GPL should recognize that most other free software licenses also permit

such linking. 

\section{GPLv3~\S14: So, When's GPLv4?}

% FIXME Say more

No substantive change has been made in section 14. The wording of the section

has been revised slightly to make it clearer.

% FIXME; proxy

In the effort to allow certain proprietary derivative works and prohibit

others, LGPL distinguishes between two classes of derivative works:

``works based on the library,'' and ``works that use the library.''  The

distinction is drawn on the bright line of binary (or runtime) derivative

works and source code derivatives. We will first consider the definition

of a ``work that uses the library,'' which is set forth in LGPLv2.1~\S5.

We noted in our discussion of GPLv2~\S3 (discussed in

compiled and linked with GPL'd software are derivative works of that GPL'd

software. This includes both linking that happens at compile-time (when

the binary is created) or at runtime (when the binary -- including library

and main program both -- is loaded into memory by the user). In GPL,

binary derivative works are controlled by the terms of the license (in GPLv2~\S3),

and distributors of such binary derivatives must release full

corresponding source\@.