I don't think there is currently a Backgammon app for Maemo. If you can find a version that's suitable for porting (open source, Linux-based python,, etc.) you may be able to coax (or offer a bounty to) a developer into doing the work.

There is a "suitable" app that analyzed Backgammon games, but I don't know if it was actually playable:

http://directory.fsf.org/project/gnubg/

There may be something else out there, though.

Tim