User Manual

49
LGPLv2.1 / LGPLv2.1+ to GPLv2 / GPLv2+ to LGPLv2 / LGPLv2+
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 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 specified 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 fits 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.