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Appendix F Open Software Announcements
P-2612HNU-Fx User’s Guide
388
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.