You'd be hard pressed to find a Swift project that doesn't depend on Apple's proprietary Foundation because Swift needs it to talk to the world!
I don't understand what IBM is thinking.
Is there any library for cross platform asynchronus IO?
For networking, Kitura uses Kitura-net, which uses BlueSocket, which in turn uses C library's sockets[1]. On GNU/Linux, this is the GNU C Library, for which a package (Glibc) is provided by the Swift port[2].
For asynchrony they seem to be using libdispatch despite it being "early in the development"[3], but I've also noticed they're wrapping epoll and curl (see 1.B again), so it's hard to gauge the real extent of the hack.
[1]: https://github.com/IBM-Swift/Kitura/blob/master/Package.swif...
https://github.com/IBM-Swift/Kitura-net/blob/master/Package....
https://github.com/IBM-Swift/BlueSocket/blob/master/Sources/...
Of course, a core Swift library for URL handling is important! And on macOS/iOS it can be implemented on top of Foundation. But I don't think that library should come with a bunch of geometry, collections, or number formatting types as well. µframeworks are Swifty. The SPM documentation says something like "in general more modules is better than fewer modules", so it's weird to have a giant framework as an official core library.