User's Manual
144
applies to certain designated libraries, and is quite dierent from the ordi-
nary General Public License. We use this license for certain libraries in order
to permit linking those libraries into nonfree 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 there-
fore permits such linking only if the entire combination ts its criteria of free-
dom. 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 compet-
ing non-free programs. These disadvantages are the reason we use the or-
dinary 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 stan-
dard. 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 where-
withal to run that program using a modied version of the Library.
The precise terms and conditions for copying, distribution and modication
follow. Pay close attention to the dierence 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 or-
der to run.