The script "TDForum" available for $19.99 at
http://www.tdscripts.com/tdforum.shtml has a security hole big enough to drive a truck through (it allows unchecked javascript to be posted into the messageboard).
BUT, and get this, TDavid's "supposed" online demo of the program at
http://www.tdscripts.com/tdforum/ DOESN'T have this security flaw!
In other words, the demo is what you want, what you buy is broken...