What does Github write that uses Swift? I thought they didn't have an iOS app and I figured their desktop app was some node-webkit or electron based thing based on it being 27mb download.
Swift is on track to be a general purpose language not only targeted towards iOS, OSX, tvOS, and Watch. There are already web servers written in Swift[1] so using Swift for backend work is increasingly more viable. They may have internal plans to implement some new products in Swift, but who knows.
My feeling is that they want a guide up now from the beginning before they proceed with creating Swift apps.
With Swift now open source and is an increasingly popular language to write brand new apps on Apple's platforms which consistent of iOS, OS X, watchOS, and tvOS.
The desktop app contains lots of Objective-C and Swift code. You can check it using `otool -o` on the binary to dump the __OBJC segment, or by opening it in Hopper.
