\chapter{The Lesser GPL}

As we have seen in our consideration of the GPL, its text is specifically

software was itself released under GPL when distributed.  Reaching as far

as copyright law will allow is the most direct way to reach that goal.

However, while the strategic goal is to bring as much Free Software into

dictate different means.  Extending the copyleft effect as far as

copyright law allows is not always the most prudent course to the goal.

In particular situations, even those of us with the goal of building a

The first example that FSF encountered where such altered tactics were

needed was when work began on the GNU C Library.  The GNU C Library would

be (and today, now is) a drop-in replacement for existing C Libraries.  On

an essential component for all programs.  It is extremely difficult to

construct a program that will run with ease on a Unix-like operating

system without making use of services provided by the GNU C Library --

all user application programs that run on any modern Unix-like system must

make use of the C Library.

By the time work began on the GNU implementation of the C Library, there

Every proprietary Unix vendor had one, and many third parties produced

smaller versions for special purpose use.  However, our goal was to create

a C library that would provide equivalent functionality to these other C

GNU/Linux systems.  However, the outcome is a bit more subtle.  In a world

where many C Libraries already exist, many of which could easily be ported

to GNU/Linux, a GPL'd glibc would be unlikely to succeed.  Proprietary

anyone who wished to write proprietary software for GNU/Linux systems.

The de-facto standard for C libraries on GNU/Linux would likely become not

glibc, but the most popular proprietary one.

The Lesser GPL was first conceived to handle this scenario.  It was clear

that the existence of proprietary applications for GNU/Linux was

new one under GPL would not stop that tide.  However, if the new C library

were released under a license that (a) permitted proprietary applications

to link with it, but (b) made sure that the library itself remained Free,

the C library.

There was no way the license of glibc could stop or even slow the creation

restrictions on the licensing of glibc was able to ensure that nearly all

proprietary applications at least used a Free C library rather than a

proprietary one.  This trade-off is central to the reasoning behind the

\section{What's the Same?}

discussion of the LGPL, we will first eliminate the sections that are

identical, or that have the minor change of changing the word ``Program''

to ``Library''.

LGPL's \S 11 is GPL's \S 7.  As discussed, it is used to ensure that

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

licenses, and requires that distribution be halted if such a trump is

known to exist.

LGPL's \S 12 adds the same features as GPL's \S 8.  These sections are

used to allow original copyright holders to forbid distribution in

licenses.

LGPL's \S 13 sets up FSF as the steward of the LGPL, just as GPL's \S 9

12.

Thus, as we see, the entire latter half of the license is identical.

are the same.  It is our intent that the two licenses operate under the

We strike a difference only in the early portions of the license.

Namely, we go into deeper detail of granting various permissions to

create derivative works, so the redistributors can make some proprietary

derivatives.  Since we simply do not allow the license to stretch as far

as copyright law does regarding what derivative works must be relicensed

we will allow to be proprietary.  Thus, we'll see that the front matter

of the LGPL is a bit more wordy and detailed with regards to the

permissions granted to those who modify or redistribute the software.

Most of LGPL's Preamble is identical, but the last seven paragraphs

introduce the concepts and reasoning behind creation of the license,

we began our consideration of LGPL\@.

In short, FSF designed LGPL for those edge cases where the freedom of the

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,

\S 3), and distributors of such binary derivatives must release full

we wish to permit.  This scenario, defined in LGPL as ``a work that uses

the library'', works as follows:

\newcommand{\workl}{$\mathcal{L}$}

\newcommand{\lplusi}{$\mathcal{L\!\!+\!\!I}$}

  \worki{}, that makes interface calls (e.g., function calls) to the

  LGPL'd work, called \workl{}, whose copyright is held by some other

  party.  Note that since \worki{} and \workl{} are separate and

  holder with regard to the licensing of \worki{}, at least with regard to

  the source code.

We will talk about the specific restrictions LGPL places on ``works that

use the library'' in detail in Section~\ref{FIXME}.  For now, focus on the

logic related to how the LGPL places requirements on the license of

and that in Section~\ref{separate-and-independent}, which discussed the

Effectively, what LGPL is doing is saying that when a new work is

In addition, the only reason that LGPL has any control over the licensing

of a ``work that uses the library'' is for the same reason that GPL has

because the {\em binary combination\/} (\lplusi{}) that must be created to

make the separate work (\worki{}) at all useful is a derivative work of

the LGPL'd software (\workl{}).

Thus, a two-question test that will help indicate if a particular work is

a ``work that uses the library'' under LGPL is as follows:

\item Is the source code of the new copyrighted work, \worki{}, a

  source code from \workl{}?

\item When the source code is compiled, does it create a derivative work

  by combining with \workl{}, either by static (compile-time) or dynamic

  (runtime) linking, to create a new binary work, \lplusi{}?

If the answers to both questions are ``yes'', then \worki{} is most likely

a ``work that uses the library''.  If the answer to the first question

in the same sense that GPL does.

Most typically, one creates a ``work based on the library'' by directly

tightly integrating new software with the library.  The lines are no doubt

fuzzy, just as they are with GPL'd works, since copyright law gives us no

litmus test for derivative works of a software program.

original LGPL'd work, a specific set of works that used that library, and

a specific set of works that were based on the library.  Once such

distinctions are established, the licensing for each component can be

\section{Subtleties in Works that Use the Library}

compilation process where the legal implications are different.

Specifically, while we know that a ``work that uses the library'' is one

whose final binary is a derivative work, but whose source is not, there

and final binary --- is a derivative work created by copying verbatim code

from the LGPL'd software.

sometimes places literal portions of the copyrighted library code into the

scenario, the derivative would not be created until final assembly and

derivative work is created.

LGPL's \S 5, \P 4 is designed to handle this specific case.  The intent of

the library does not in itself cause the compiled work to be a ``work

based on the library''.  However, since the compiler copies verbatim,

copyrighted portions of the library into the object code for the otherwise

``work based on the library''.  It is not FSF's intent that a mere

compilation idiosyncrasy changes the requirements on the users of the

LGPL'd software.  This paragraph removes that restriction, allowing the

As it turns out, we have only once had anyone worry about this specific

idiosyncrasy, because that particular vendor wanted to ship object code

(rather than final binaries) to their customers and were worried about

primarily to quell the worries of software engineers who understand the

level of verbatim code copying that a compiler often does, and to help

them understand that the full implications of LGPL are the same regardless

course, it only requires that source code for the library itself be made

available.  The work that ``uses'' the library need not be provided in

source form.  However, there are also conditions in LGPL \S 6 to make sure

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\chapter{Integrating the GPL into Business Practices}

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