Not really - they're just swapping out the libraries for ones that they can use on iOS. It's not going to be portable off of iOS, etc. (EDIT: That is, the iOS specific UI code - obviously non-platform specific library based code will be completely portable)

Plus it won't be as fast as writing it in C/obj C as it will have garbage collection overhead, type checking, bounds checking, etc etc. (For iOS style UI apps this isn't a concern as they're mostly just thick clients to real calculations done elsewhere, so speed barely matters as you are just relying on the speed of UIKit for graphics anyway.)