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GNU LESSER GENERAL PUBLIC LICENSE
Version 2.1, February 1999
Copyright (C) 1991, 1999 Free Software Foundation, Inc.
59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.
[This is the fi rst released version of the Lesser GPL. It also counts as the
successor of the GNU Library Public License, version 2, hence the
version number 2.1.]
Preamble
The licenses for most software are designed to take away your freedom
to share and change it. By contrast, the GNU General Public Licenses
are intended to guarantee your freedom to share and change free
software--to make sure the software is free for all its users.
This license, the Lesser General Public License, applies to some
specially designated software packages--typically libraries--of the Free
Software Foundation and other authors who decide to use it. You can
use it too, but we suggest you fi rst think carefully about whether this
license or the ordinary General Public License is the better strategy to
use in any particular case, based on the explanations below.
When we speak of free software, we are referring to freedom of use, not
price. Our General Public Licenses are designed to make sure that you
have the freedom to distribute copies of free software (and charge for
this service if you wish); that you receive source code or can get it if you
want it; that you can change the software and use pieces of it in new free
programs; and that you are informed that you can do these things.
To protect your rights, we need to make restrictions that forbid
distributors to deny you these rights or to ask you to surrender these
rights. These restrictions translate to certain responsibilities for you if
you distribute copies of the library or if you modify it.
For example, if you distribute copies of the library, whether gratis or for
a fee, you must give the recipients all the rights that we gave you. You
must make sure that they, too, receive or can get the source code. If you
link other code with the library, you must provide complete object fi les
to the recipients, so that they can relink them with the library after
making changes to the library and recompiling it. And you must show
them these terms so they know their rights.
We protect your rights with a two-step method: (1) we copyright then
library, and (2) we offer you this license, which gives you legal
permission to copy, distribute and/or modify the library.
To protect each distributor, we want to make it very clear that there is no
warranty for the free library. Also, if the library is modifi ed by someone
else and passed on, the recipients should know that what they have is not
the original version, so that the original author’s reputation will not be
affected by problems that might be introduced by others.
Finally, software patents pose a constant threat to the existence of any
free program. We wish to make sure that a company cannot effectively
restrict the users of a free program by obtaining a restrictive license
from a patent holder. Therefore, we insist that any patent license
obtained for a version of the library must be consistent with the full
freedom of use specifi ed in this license.
Most GNU software, including some libraries, is covered by the
ordinary GNU General Public License. This license, the GNU Lesser
General Public License, applies to certain designated libraries, and is
quite different from the ordinary General Public License. We use this
license for certain libraries in order to permit linking those libraries into
non-free programs.
When a program is linked with a library, whether statically or using a
shared library, the combination of the two is legally speaking a
combined work, a derivative of the original library. The ordinary
General Public License therefore permits such linking only if the entire
combination fi ts its criteria of freedom. The Lesser General Public
License permits more lax criteria for linking other code with the library.
We call this license the “Lesser” General Public License because it does
Less to protect the user’s freedom than the ordinary General Public
License. It also provides other free software developers Less of an
advantage over competing non-free programs. These disadvantages are
the reason we use the ordinary General Public License for many
libraries. However, the Lesser license provides advantages in certain
special circumstances.
For example, on rare occasions, there may be a special need to
encourage the widest possible use of a certain library, so that it becomes
a de-facto standard. To achieve this, non-free programs must be allowed
to use the library. A more frequent case is that a free library does the
same job as widely used non-free libraries. In this case, there is little to
gain by limiting the free library to free software only, so we use the
Lesser General Public License.
In other cases, permission to use a particular library in non-free
programs enables a greater number of people to use a large body of free
software. For example, permission to use the GNU C Library in non-free
programs enables many more people to use the whole GNU operating
system, as well as its variant, the GNU/Linux operating system.
Although the Lesser General Public License is Less protective of the
users’ freedom, it does ensure that the user of a program that is linked
with the Library has the freedom and the wherewithal to run that
program using a modifi ed version of the Library.
The precise terms and conditions for copying, distribution and
modifi cation follow. Pay close attention to the difference between a “work
based on the library” and a “work that uses the library”. The former
contains code derived from the library, whereas the latter must be
combined with the library in order to run.