[[...it could actually run a VoIP wifi app, several of which already exist for OS X, and thus leave them on the bad side of convergence...]] Let us also remember the fine line Apple is walking with the "iPhone" name. Cisco already has a VOIP iPhone, and if Apple wants to use the name then they have to be able to show a judge (and Cisco) that the iPhone CAN NEVER use VOIP and thus compete with Cisco. I suspect this lockdown has less to do with Apple's revenue stream vis-a-vis 3rd party developers, and more to do with ensuring they can navigate the legal jungle of the telephone world without worry.