According this article: * http://blog.krisk.org/2013/09/apples-new-facetime-sip-perspective.html http://blog.krisk.org/2013/09/apples-new-facetime-sip-perspe..

According this article: * http://blog.krisk.org/2013/09/apples-new-facetime-sip-perspective.html http://blog.krisk.org/2013/09/apples-new-facetime-sip-perspe... ... FaceTime is more or less SIP hacked to work better with the crummy Internet we have to contend with these days. So we probably know enough to make something compatible. What we don't have is any assurance that Apple would allow such interoperation going forward. The problem is not actually technical...