I don't think that is the point. I am pretty sure the author was using the CLR as an example. You could write WPF applications using F#, IronPython, or IronRuby

I don't think that is the point. I am pretty sure the author was using the CLR as an example. You could write WPF applications using F#, IronPython, or IronRuby because the are all compile CLR code. If the most popular languages on Mac and Linux all compiled down to LLVM they would be a lot more inter-operable like the CLR languages. It would be much easier to leverage the Cocoa framework from Python, Lisp, or Java if all were build on the LLVM (or the HLVM which is built on the LLVM).