The purpose of this License is to make a manual, textbook, or
other written document "free" in the sense of
freedom: to assure everyone the effective freedom to copy and
redistribute it, with or without modifying it, either
commercially or noncommercially. Secondarily, this License
preserves for the author and publisher a way to get credit for
their work, while not being considered responsible for
modifications made by others.
This License is a kind of "copyleft", which means
that derivative works of the document must themselves be free in
the same sense. It complements the GNU General Public License,
which is a copyleft license designed for free software.
We have designed this License in order to use it for manuals for
free software, because free software needs free documentation: a
free program should come with manuals providing the same
freedoms that the software does. But this License is not limited
to software manuals; it can be used for any textual work,
regardless of subject matter or whether it is published as a
printed book. We recommend this License principally for works
whose purpose is instruction or reference.
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