I based the design on phpBB for a few reasons. Most of all, I wanted to use a familiar conventional forum layout. I want it to look like a forum immediately, and easy to use for people who have used forums in the past. Second, there is a large open source theme repository for phpBB themes, making it easier to change the layout of MT Forum (that said, unfortunately the process turns out to be not as simple as I would have liked). Finally, the new phpBB layout does not use HTML tables in the markup, and I like that a lot.
