As shorts as possible I am intending to make an online game in php (which I'm pretty familiar with) and I want to have it use a 'styles' system (at key points in the game the style will actually change automatically, but users may have options as well should they prefer), and phpBB 2.0.x has a templating system which would make that very easy indeed, a few other nifty features as well I could probably use. As far as an online game goes 2.2 doesn't really offer anything extra (no offense).
Well, what I'm hoping is that since phpBB 2.0.x is open source (and 2.2 will be as well) I could borrow elements from the templating system? I doubt much would be directly copied, but many things would be very useful if I am allowed to do so. Similar with a few other features such as the database management allowing multiple types to be used. The game is likely going to be an open source thing people can host and mod themselves since I don't really have the cashflow to host it if it becomes popular.
So, can I use phpBB 2.0.x code for this kind of thing without having some huge legal smackdown on me? I would of course give full credit (and would probably use phpBB for support forums
) 
).