You can wrap native UI libraries with just about every language in existence. That's not what people usually mean when they say "native" though. I think they mean precompiled to a binary for a specific architecture.

yeah you can. The whole native vs non native is about whether the UI is native and directly integrates with the platform, not the language or whether there is a runtime.

Err, well the article is about using Mono with GTK, which is not native outside of Gnome.

That's why you'd use monomac, mono touch or wpf on osx,iOS and windows, respectively. Xamarin also has a solution for android.