"It is a symbol of Irish art. The cracked lookingglass of a servant." -- James Joyce
I don't think I buy/understand Shah's argument that self-ownership is an incoherent concept. By way of analogy, I could imagine someone claiming that the concept of God is incoherent because God is supposed to be self-caused, and it is incoherent for something to be the cause of itself. I don't think that's right. Sure, most things have a cause other than themselves, but that doesn't mean that self-causation is conceptually impossible. Likewise, most things do not own themselves, but that alone doesn't make self-ownership conceptually impossible. A better argument, I think, is that if a person really did own himself, then he ought to be able to sell himself (part of being the owner of something is the right to sell it). Rothbard, however, explicitly says that you aren't allowed to sell yourself. So either you don't really own yourself, or ownership doesn't necessarily imply the right to sell the thing you own (with all that this implies).
I would say God is uncaused rather than self-caused. "I am that I am" and all.I don't know if incoherent is quite right, but owning oneself has always seemed to me like marrying oneself.