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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.
TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND
MODIFICATION
0. This License Agreement applies to any software library or other program which contains a
notice placed by the copyright holder or other authorized party saying it may be distributed under
the terms of this Lesser General Public License (also called “this License”). Each licensee is
addressed as “you”.
A “library” means a collection of software functions and/or data prepared so as to be
conveniently linked with application programs (which use some of those functions and data) to
form executables.
The “Library”, below, refers to any such software library or work which has been distributed under
these terms. A “work based on the Library” means either the Library or any derivative work under
copyright law: that is to say, a work containing the Library or a portion of it, either verbatim or
with modifications and/or translated straightforwardly into another language. (Hereinafter,
translation is included without limitation in the term “modification”.)
“Source code” for a work means the preferred form of the work for making modifications to it. For
a library, complete source code means all the source code for all modules it contains, plus any
associated interface definition files, plus the scripts used to control compilation and installation of
the library.
Activities other than copying, distribution and modification are not covered by this License; they
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