At least one company is seeing the silver lining in Apple’s decision to deprecate UDIDs, or unique ID numbers that developers use to track users across apps.

OpenFeint says it’s launching a single sign-on service for social games as a replacement later this fall. The company says the project, dubbed OFUID, will become a universal account system that criss-crosses platforms. So the same person who plays a game on Android and on iOS won’t be counted twice.

Since OpenFeint already gives users individual accounts so they can compete against friends, it’s not a huge leap for the company to build an ID and single sign-on system. If developers get permission from players to see their OFUID, then they can look at user behavior across games.

There are a few caveats to consider, however. OpenFeint wasn’t authenticating access to its API earlier this year and a New Zealand-based security specialist was able to use his UDID and OpenFeint’s API to expose his location, his account name and Facebook profile picture URL, which could have been used to discover his real name. OpenFeint fixed the security hole and presumably will take privacy very seriously with OFUID. However, this is not a good track record to start from.

Apple said it would deprecate UDIDs in iOS 5 after privacy concerns about the system were widely publicized in the media. Apple is instead asking developers to create unique user identifiers that are specific to their apps. Some developers have also talked about using the MAC address, which is a unique hardware ID that’s assigned to all devices connected to the web.

The other part of what OpenFeint’s announcing is an install trade program, which is interesting because it shows the company is trying to strengthen its direct relationships with consumers. OpenFeint will guarantee developers 1.5 new installs for every new install of Game Channel, a free-app-a-day vehicle.

OpenFeint is the largest pure mobile-social gaming network on iOS and it says it has 115 million users worldwide. It was able to acquire that many players because of the way it was designed as a social layer that other game developers could quickly install to give players features like social leaderboards.

But it also means that while millions of people have registered with the service, many of these players may not interact much with OpenFeint’s services directly on a regular basis. Having a direct, consumer-facing app would create more revenue opportunities for OpenFeint, which lost $6.6 million through the 2010 fiscal year.