License
GNU Free Documentation License Version 1.1
This book is available under the GNU Free Documentation License. You can copy, distribute and modify it under the terms of the GFDL.
GFDL
license family
Using books under the GNU Free Documentation License Version 1.1
The 3 books in this list are available under the GNU Free Documentation License Version 1.1. The license tells you what you can do with the text: read it, share it, remix it or use it commercially. Always check the license page linked above, because the exact terms and attribution requirements matter.
If you plan to reuse a book in a course, a translation or a commercial product, keep the attribution notice and link back to the original source. When in doubt, contact the author or publisher.