I doubt 15k is really an issue for Apple. You could even say that at its scale its Apple's duty to pay that membership and give back contributing to the specifi

I doubt 15k is really an issue for Apple. You could even say that at its scale its Apple's duty to pay that membership and give back contributing to the specifications. Using standards has some advantages like not having to test dozens of authentication systems/clients doing basically the same thing. If you would have read the document you would have found that you can't use standard openID clients due some issues with Apple's implementation. Some of the issues have security implications.