Copyright law looks like the only reference point for defining "write" - if you own copyright for something, you "wrote" it, otherwise you legally didn't (even if you claim otherwise). It might have been much simpler if Apple just said "all applications should be products of the iPhone SDK tools".

Anyway, it all depends on what exactly they want to accomplish with this clause and it is poorly worded at the moment for whatever that purpose be. Hope Apple clarifies soon.