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.
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