XAML is just a way of writing object graphs in XML. It is not tied to WPF or anything (heck, we use it to represent user data and style information within GraphML).
And yes, XAML is used by more than WPF at this point (Silverlight, UWP, and possibly more).
Re:Visual Studio for Mac
by youdounderstand on Monday November 14, 2016 @09:43AM
(#12950043)
The markup is a pretty small part of XAML/WPF. The actual framework, controls, and rendering are the bulk of it.
PS. According to me it was difficult to port the Graphic part of WPF to Linux/Mac.