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
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 are
outside its scope. The act of running a program using
the Library is not restricted, and output from such a
program is covered only if its contents constitute a
work based on the Library (independent of the use of
the Library in a tool for writing it). Whether that is true
depends on what the Library does and what the
program that uses the Library does.
You may charge a fee for the physical act of
transferring a copy, and you may at your option offer
warranty protection in exchange for a fee.
?a) The modified work must itself be a software
library.
?b) You must cause the files modified to carry
prominent notices stating that you changed the files
and the date of any change.
?c) You must cause the whole of the work to be
licensed at no charge to all third parties under the
terms of this License.
?d) If a facility in the modified Library refers to a
function or a table of data to be supplied by an
application program that uses the facility, other than
as an argument passed when the facility is invoked,
then you must make a good faith effort to ensure that,
in the event an application does not supply such
function or table, the facility still operates, and
performs whatever part of its purpose remains
meaningful.
(For example, a function in a library to compute
square roots has a purpose that is entirely well-
defined independent of the application. Therefore,
Subsection 2d requires that any application-supplied
function or table used by this function must be
optional: if the application does not supply it, the
square root function must still compute square roots.)
These requirements apply to the modified work as a
whole. If identifiable sections of that work are not
derived from the Library, and can be reasonably
considered independent and separate works in
themselves, then this License, and its terms, do not
apply to those sections when you distribute them as
83
