Hey David. Sorry for the rushed merger, I'll be sending out an email to Droiders shortly.
But to answer your question, it's a custom format. We used to be phpBB (you came from vB) but frankly we think either forum software is a bloated mess and we made our own.
It's messy too, because it's unfinished, but once you get used to it it's a lot
cleaner, faster and more usable than vB.