It's not too hard to cobble together open-source headers and autogenerated minimally viable headers for the OS frameworks (this is what the initial non-official

It's not too hard to cobble together open-source headers and autogenerated minimally viable headers for the OS frameworks (this is what the initial non-official iPhone toolchains did). They'll be very incomplete, however, quite a bit of software will not build correctly, and it will take a significant effort to clean them up.