http://www.gnu.org/licenses/fdl.txt
Copyright (C) 2000,2001,2002 Free Software Foundation, Inc.
51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
0. PREAMBLE

The purpose of this License is to make a manual, textbook, or other functional and useful 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.
GNU Free Documentation License
Version 1.2, November 2002