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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
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The precise terms and conditions for copying, distribution and modification follow. Pay close attention to the difference
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TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
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(For example, a function in a library to compute square roots has a purpose that is entirely well-defined
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28
English
GNU LESSER GENERAL PUBLIC LICENSE
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