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.