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GNU LESSER GENERAL PUBLIC LICENSE
Version 2.1, February 1999
Copyright (C) 1991, 1999 Free Software Foundation, Inc.
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is
not allowed.
[This is the first 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 first 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 files 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 the 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 modified 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 licen-
se 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 specified in this license.
Most GNU software, including some libraries, is covered by the ordinary GNU General Public License.
