If you are interested in a free, open source, simple and very configurable forum/message board; hop over to:

http://kabal-net.com/

No code is available yet, but it soon will be @ sourceforge. If you would like to help develop it further, we are also looking for others to join the scene.

If you go the "Programming" board you will find a section for kncForum. Feel free to post any bugs you find. Thanks.