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1. Introduction to the Licenses {#introduction-to-the-licenses .chapter}
===============================

@firstcopyingnotice{{Copyright © 2010 Free Software Foundation, Inc.\
 {This essay is published in @fsfsthreecite} Written by Brett Smith and
Richard Stallman.\
 This part contains the text of the latest versions of the primary GNU
licenses: the GNU General Public License (GNU GPL), the GNU Lesser
General Public License (LGPL), and the GNU Free Documentation License
(FDL). Though they are legal documents, they belong in this book of
essays because they are concrete expressions of the ideals of free
software.

Software development for the GNU operating system began in 1984. Once
Richard Stallman had parts of the GNU system that were worth releasing,
he needed a license to release them under. Some free software licenses
already existed; these gave users permission to modify and redistribute
the software, but they also allowed using the code in proprietary
versions and proprietary programs. Using those licenses, GNU would have
failed to achieve its goal of delivering freedom to all users, because
middlemen would have converted the GNU code into proprietary software.

So Stallman devised a license to assure every user the freedom to modify
and redistribute the software. It granted these permissions under one
key condition: whoever distributed the software must pass along the
authorization to modify and redistribute that same software, along with
the source code making it practical to do so. Stallman coined the term
“copyleft” (see “What Is Copyleft?” on @pageref{Copyleft}) to describe
this key twist of using the legal power of copyright to ensure freedom
for all users.

GNU copyleft licenses were first developed for software, and later for
related areas such as software documentation. In them, the principles of
the free software movement, explained throughout the essays in this
book, take practical form. Each of their successive revisions has had to
wrestle with free software’s legal and practical obstacles and offers
numerous illustrations of how free software ideals are codified into
legal terms.

### The Origins of the GPL {#the-origins-of-the-gpl .subheading}

The first version of the GNU General Public License was published in
1989—but Stallman had been releasing software under copyleft licenses as
part of the GNU Project since as early as 1985. Prior to 1989, each
published GNU program had been covered by a license specifically
tailored for it. Instead of a single GNU General Public License, there
was a GNU CC General Public License, a GDB General Public License, and
so on. These licenses were identical except for minor differences: for
instance, terms about displaying license notices to users were different
for different programs and, unless it covered a program that was just
one source file, each license contained the name of the program it
applied to.

By 1989, Stallman had had enough experience with different GNU packages
under slightly different licenses to conclude that it was crucial to
unify them into one license that would cover all these packages. He
worked with Jerry Cohen, an attorney at Perkins Smith & Cohen LLP, to
collect concepts from all the different licenses written up to that
point, and bring them together into one license. It was thus that on
1 February 1989 the GNU General Public License was born.

The first version of the license sought to ensure two results: first,
that all derived works of the software would be released under the same
license and, second, that everyone who received the software would have
a chance to get the source code. These requirements implement a strong
copyleft by blocking the three main ways of making programs proprietary:
with copyright, with end-user license agreements, and by not
distributing source code.

In comparison to the program-specific licenses that had preceded it, GPL
version 1 featured few substantial changes—the GPL was evolutionary, not
revolutionary—but it made a big practical difference. Previously,
developers who had wanted to copyleft a program had needed to tailor one
of the existing licenses to that program. Many had not bothered. With
the release of the GPL, those developers had a license they could use
out of the box to provide all of their users with freedom to share and
change the software. It was a powerful tool.

### Version 2 {#version2 .subheading}

After the 1981 US Supreme Court decision in Diamond v. Diehr, the US
Patent and Trademark Office began issuing patents for software. Software
patents threaten free software and proprietary software alike (see part
IV in this book), and Stallman realized that they could subvert the
copyleft in the GNU GPL.

By selectively issuing patent licenses, patent holders can arbitrarily
control how the software under them is distributed or modified. A patent
holder can give one party permission to resell the program, another
permission to develop and use a modified version at her company, and a
third permission to do all the activities that the GPL itself allows.
They can demand whatever they wish in exchange for these permissions.
They have this power over any software that implements the patented
idea, whether or not they have modified or distributed it themselves.
This power threatens free software because third parties with patents
can impose restrictions on free software users and developers.

If patent holders don’t distribute or modify software, then a software
license based on copyright like the GPL can’t control their activities:
they haven’t done anything that requires permission under the license.
But the software license can stop each of the program’s distributors
from entering limiting agreements with the patent holder. Enter GPL
version 2: a new section in the license (sec. 7) explicitly says that if
parties are subject to other legal agreements—such as a patent
license—that contradict the GPL’s terms, then the licensee must refrain
from distributing the software at all. As a result, any party that wants
to distribute or modify the software, and also obtain a patent license,
must ensure that the terms of that license are consistent with all of
the GPL’s conditions: recipients of the software must receive it under
the same terms, with no additional restrictions, and have the means to
get the source code.

This new section protected the integrity of the distribution system for
GPL-covered software. A fundamental principle of the license is that
every licensee, from the most humble individual to the largest
corporation, has the exact same rights to share and change the software.
Patent holders who do not distribute the software themselves and
selectively issues patent licenses could potentially interfere with this
goal, splitting licensees into different groups however they see fit.
Section 7 of GPL version 2 prevents this abuse.

### The LGPL {#the-lgpl .subheading}

The GPL worked well for the programming tools, utilities, and games that
were released by the GNU Project in the early years; however, Stallman
recognized that releasing the recently developed GNU C Library the same
way could backfire. Aside from some extensions, the GNU C Library was to
be a compatible replacement for the Unix C Library, so any C program
would be able link with either one. If proprietary C programs were not
allowed to use the GNU C Library, they would simply use the Unix
library. Being strict in this case would gain nothing.

Stallman decided to compromise with a modified copyleft: one that would
protect the freedom of the library itself, but not that of the programs
that use it. This idea was implemented in a license originally called
the GNU Library General Public License, first published as version 2.0,
in June 1991. The original LGPL stated Conditions like the GPL’s—with an
important exception: if someone else’s program used the library only by
referring to it as a library, that program’s source could be distributed
under license terms of the author’s choosing. However, the executable
made by combining the program and the library had to come with a copy of
the LGPL and source code for the library, and provide some mechanism for
users who have modified the library to update the executable to use
their modified library.

How does a developer use the work as a library in order to take
advantage of the special set of conditions provided by LGPLv2? Think of
a computer program as a series of instructions for doing a particular
job: compiling or linking the program with a library provides the
programmer with a means to say, “When the program gets to this point,
get further instructions from the library, and come back here when those
are done.” Libraries are commonly used in software development because
they make the effort less repetitive and less error prone: programmers
don’t have to reinvent the wheel—and perhaps introduce bugs in the
process—every time they want to accomplish a particular task. Because
libraries are so widely created and used, developers have the means to
readily take advantage of the LGPL’s additional permissions.

Version 2.0 of the license worked as intended: in some situations,
proprietary software developers chose to use an LGPL-covered library
over a proprietary alternative, and users received the freedom to share
and change that library. This did not produce an “ideal” outcome—where
the user had complete control over the entire program—but in these cases
the GPL would not have achieved that ideal outcome either. The LGPL
assured the users some freedom where they would have otherwise had none.

The name “Library GPL” led some free software developers to assume all
libraries ought on principle to be licensed this way, but that was not
the intent—when a free library has no proprietary competitor, releasing
it under the GNU GPL can benefit free software. To avoid this unintended
message, Stallman renamed this license to the Lesser General Public
License, and incremented the version number to 2.1 to reflect the
relatively minor changes in the text: the license sported a new
preamble, a few wording clarifications, and allowed programs to make
their calls to the library through special system facilities for shared
libraries where those are available. The Lesser General Public License
version 2.1 was released in February 1999.

### The FDL {#the-fdl .subheading}

At the turn of the century, free software was growing much faster than
it had been previously; the documentation, however, was not keeping
pace. Stallman was concerned about this failure and wrote about it in
“Free Software Needs Free Documentation” (@pageref{Free Doc}).

While there are some similarities between software and
documentation—they are both works that are meant for practical use—there
are important differences in the ways they can be used. The GPL and the
LGPL were not suitable for manuals.

For some time, GNU packages had been using an untitled, simple, ad hoc
copyleft license for each manual. Since each manual’s license was
different, text could not be copied from one manual to another. So
Stallman wrote the GNU Free Documentation License, a copyleft license
designed primarily for software documentation and other practical
written works.

The FDL was first published in March 2000. The principles of the
copyleft remain the same: everyone who receives a copy of the work
should be able to modify and redistribute it. Where the FDL differs from
the software licenses is in the details of its implementation:
conditions about how to attribute the work and provide “source code”—an
editable version of the document—are different.

### Version 3 {#version3 .subheading}

During the 1990s, as free software became more popular, the GPL emerged
as the clear copyleft license of choice for the community, and was
adopted by the majority of free software projects; at the same time,
however, proprietary developers had come up with methods of effectively
denying users the freedoms that the GPL was meant to protect, without
actually violating the GPL. In addition, there were other practices that
the GPL did not handle conveniently. To deal with these issues called
for an updated version of the license.

Around 2002, Stallman and others at the Free Software Foundation began
discussing how to update the GPL, and the LGPL along with it. The FSF
established a public review process, run with help from attorneys at the
Software Freedom Law Center, to catch possible problems before actually
releasing the new licenses. Committees of advisors from the community
studied issues raised by public comments and reported the various
positions and arguments to Stallman, who decided what policy to adopt;
then he wrote license text with advice and suggestions from the
attorneys. The importance of the changes made are explained in “Why
Upgrade to GPLv3” (@pageref{Why V3}).

Version 3 used new terminology to promote uniform interpretations in
different jurisdictions, and modified some requirements to fit new
practices in the free software community. Beyond that, it introduced
several new conditions to strengthen the copyleft and thereby the free
software community as a whole. For instance, it

-   blocked distributors from restricting users by building hardware
    that rejects the users’ modified versions (“tivoization”);
-   allowed code to carry limited additional requirements, for
    compatibility with some other popular free software licenses;
-   and strengthened patent requirements by providing clear terms to
    handle patent cross-licenses, which are common arrangements between
    large patent-holding companies.

Both GPLv3 and LGPLv3 included terms to address all of these issues, and
were finally released on 29 June 2007. These licenses are the state of
the art in copyleft, going farther than any other software license to
protect users’ freedom and bring about a world in harmony with the
ideals expressed in this book.

@endgroup

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