I
GNU
Lesser
General
Public
License
(LGPL)
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 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.
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.
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