Indeed. I don't think Apple would open source Foundation, App Kit, UI Kit, and a bunch of other things; that by itself precludes inclusion with Swift. Aside from that, a lot of those things rely on the full version of Core Foundation in C; I think the (open source, non-Swift) implementation of Core Foundation, CF Lite, is heavily reduced compared to what ships with Apple's OSs and would make an ineffective base for redundantly reimplementing those frameworks on other systems.