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.
Take our 
