The name of this software is ubbthreads. It was originally called wwwthreads and available as both a perl... and PHP version, but was purchased by a company called Infopop and is now only PHP.

They promise a completely rewritten version (if you saw how they designed this, you'd be amazed) sometime in the next few months. I've also considered switching over to the other large, popular message board software, vBulletin. But for now, we'll stick with this...

DocJohn