Apple has rejected an iPhone application that supposedly uses off-limits technology just like Google's mobile application--only the developer swears it's not true.
Landon Fuller, who developed a photo contact management system called Peeps, said on his blog that Apple had rejected Peeps from the App Store because, "Peeps cannot be posted to the App Store due to the usage of a non-public API. Usage of non-public APIs, as outlined in the iPhone SDK Agreement section 3.3.1, is prohibited." The thing is, Fuller insists that Peeps does not use any programming tools but the public ones Apple exposes to developers as part of the iPhone SDK, saying "the last thing I would do is deliver time-bomb code to a paying customer." (Thanks to Daring Fireball for the link.)
APIs are tools that applications use to exploit parts of a computer's operating system. Operating system developers usually label some proportion of the various APIs in the OS as "public," meaning they'll support the use of those APIs well into the future to ensure applications will not break with future OS updates.
There are usually lots of other APIs lying around that the OS vendor doesn't make public, but that developers can see if they poke around a little bit. Google used such an API to trigger a voice prompt from the iPhone's proximity sensor in its Google Mobile application, which the company admitted was against the rules of the App Store.
Fuller seems to believe this is all just a misunderstanding, since his application looks an awful lot like Apple's Cover Flow feature but doesn't actually use the same implementation Apple does to display album covers in iTunes. Maybe he just needs a bigger market cap: Google Mobile is still available on the App Store, and a Google representative said he had no updates on whether Apple had ordered any changes to Google Mobile or if Google planned to make any changes on its own. An Apple representative did not return a call seeking comment, but Apple representatives have never returned any calls seeking comment about the App Store approval process.
Sometimes it really does seem that getting your iPhone application approved or rejected for the App Store comes down to whether or not you draw Inspector No. 1 or Inspector No. 2 that day.