Wild. It sounds like they're just making the systems they've already developed in their own games available to anyone who wants to use them. Right now, they're looking at a private beta (interested devs can sign up on their site), and eventually the service will be free for a limited number of users, with certain costs as the userbase grows.
The cynical side of us wonders if there's a catch in there somewhere -- presumably, all of the users in OpenFeint will keep their information on the Aurora Feint-owned server, so we'd guess there's a chance that at some point in the future, they could use that list for less-than-honorable actions (Steve Demeter's Onyx Online plan is another service that aims to be platform-wide, which seems to have similar risks). But that's just us being paranoid -- taken at face value, this just seems like one team of indie developers opening up what they've already done to help other devs. Very cool.