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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.
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 modified version of the Library.
The precise terms and conditions for copying, distribution and modification 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.
General Notes
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