Everything is freely available for use, as long as you correctly attribute my work (and don't incorrectly attribute derived works to me). Feel free to contact me if in doubt, and I'm always happy to hear about any use you're making of my work.
If you care about licensing issues, all text is available under a Creative Commons Attribution license. All computer source code is available under your choice of the MIT or BSD licenses (these are essentially the most permissive software licenses besides the public domain).
This work by Scott Morrison is licensed under a Creative Commons Attribution 3.0 United States License.