Using vBulletin as base for non-forum product

[SDB]

Hi All

I'm after some advice.

I am an experience developer, but very new to PHP. I have written a few mods for vBulletin, and am just starting to write a very large social networking project and was considering using vBulletin as the base.

The reasons :

1) The libraries for input cleaning, smilie parsing, db handling, user registration, etc, etc
2) The template system.
3) I'm comfortable with it.

The project will have almost no forum element to it whatsoever, so this seems a bit of a waste.

My questions are these..

a) is there another template system out there that works similarly to the vBulletin one? - I've been using SMARTY, but really don't feel comfortable with the way it works.
b) if I WAS to use vBulletin as a base, are there any license issues with modifying and using it in this fashion?

Thanks in advance.

Simon