You can add plugins for payments from other sources. Easiest would be Google Wallet since it's free if you already have a Gmail account. I can't recall offhand if you can get it to set member status automatically, but I know it can be done.
What is the website hosted through? Some hosts have their own donation setups through the site portals. I know the last PHPBB forum I setup was through Nuclear Fallout and they had a direct donation option through theirs.