Nobody is currently preventing this from happening and I doubt there is much Apple could do to stop it. That is to say, Openstep is an open API that anyone is free to develop an implementation of.
Of course, this isn't the same as if, for example, Sony directly circumvented or undermined Apple's security or certification technology.
> I doubt there is much Apple could do to stop it. That is to say, Openstep is an open API that anyone is free to develop an implementation of.
I am not so sure. OpenStep (the spec) is probably safe, but that doesn't make sure the rest of Cocoa (which implements a superset of OpenStep) is immune from a patent or IP-related offensive.
Of course, this isn't the same as if, for example, Sony directly circumvented or undermined Apple's security or certification technology.