Airfoil Speakers Touch Back in App Store without AirPlay Support
Rogue Amoeba has released a downgrade to Airfoil Speakers Touch, the app that enabled an iOS device to act as an AirPlay receiver. The downgrade was necessary because Apple pulled the app a few weeks ago, and the only way Rogue Amoeba could get it back in the App Store was by removing the AirPlay capabilities. Airfoil Speakers Touch can still receive audio from a Mac or a PC (and from an iOS device or iTunes through one of the above), but it can no longer appear as an AirPlay destination for iOS or iTunes directly. In this blog post, it becomes clear that Apple chose to restrict the app purely for unspecified and capricious reasons rather than any rule infractions.
I have no inside knowledge about the matter, however a possible reason why Apple might have pulled this functionality because it could be based on some work done by hackers to reverse engineer the cryptography used in AirPlay:
(again I don't know anything about how Rogue Amoeba chose to implement this feature, this is merely a possibility)
Such reverse engineering (I believe) is prohibited by Apple's developer policies; plus it is in fact a violation of the Digital Millennium Copyright Act (DMCA), since the private key that was reverse engineered is a form of encryption.
I'm not sure precisely what they did, and speculation may be futile. Apple didn't cite reverse engineering or breaking encryption either in its replies or in a note Phil Schiller sent (and that was forwarded) via email to a customer who asked him the question.
I hadn't seen the post Glenn referred to, but for those who want to see what Schiller claimed (and Rogue Amoeba refuted), check http://rogueamoeba.com/utm/2012/06/08/in-response-to-mr-schiller/