Having seen the Apple open source pages before, it was what I expected but even so I agree; with OP title it sounds like macOS 10.12 is open source in its entir

Having seen the Apple open source pages before, it was what I expected but even so I agree; with OP title it sounds like macOS 10.12 is open source in its entirety. I suggest editing the title to the following: "Open Source Components of macOS 10.12"