looks like a "hack" of Vbulletin.
there are many forum software packages that are already written. I'd recommend using them as webforums are very complex and are a real pain in the but to write. I've written a simple "message board" for a site i did, and it's paltry in comparison to what you can do with a real one.
if you need, you can get a free one at http://www.phpbb.com/ for free thats open source and customizable