Back in October, Steve Jobs explained in length how the iOS successes that Apple is enjoying have convinced them to incorporate it back to the Mac platform, and the first piece of that is the  an introduction of an App Store in OS X. Promising that the Mac App Store would be live within 90 days, this puts it at some point in January at the latest. Now, Apple is informing developers that some expected features will not be available for Mac OS apps. Namely, in-app purchases, and Game Center. This means that desktop applications will not have access to these features which have started to be common in iOS devices. Whether this is due to a delay on Apple's part, or they simply do not intend to provide these features on the Mac, is unknown as of yet.