PHPBB is basically a free forum system much like vBulletin and co. It features a powerful temnplate system which can be styled according to the user's needs. Try visiting the Official PHPBB Styles page first and seeing what downloads they have. If you need more then I'm sure Google and the PHPBB Forums will provide you with enough links to keep your friend busy.
Great forum is phpBB2 even though it gets more than it fair share of hackers attacking it. Bout the best 'hack' you can do to this forum yourself though is the 'Categories Hierarchy' one by Ptirhiik. Turns the phpBB2 forum into a Vbulletin lookalike with the ability to show forums and subcategories in an endless line. Without this hack the board is very similar to all the other forums out there. I had some working examples of this all sharing the same login but removed them forra clean up. Will have some online for demo purposes again very soon though, along with demos of loads of other types of forums too.
Must admit that having tested a great many forums I keep returning to the phpBB2 one because of the Heirachy mod. When you see it working you will understand and appreciate why for sure.