I think it's really up to Apple, the developer, and the courts to decide. Most software companies (esp. large ones) have intellectual property agreements which force you to assign ownership of anything you create on company time to the company. Employees who are paid on salary are generally always considered to be on company time, since their pay does not correspond to the number hours they spend at the office.
This really seems to lie in a gray area, and that's what courts tend to be good at settling.
(IANAL, of course).