Clean up sample BSD license in Committer's Guide to match the one in
/usr/share/examples/etc/bsd-style-copyright. There were a number of
minor wording and formatting differences. Provide it in C source
code format.

Add text talking about non-BSD licenses in the tree, including
limitations.

Add a paragraph adding strong caution when it comes to intellectual
property, pointing at the core team as a contact for any problems.