trying to resuscitate the thing
I see this as Microsoft trying to resuscitate their *FAILED* "new, shiny" UI model, aka that XAML-based abomination that ultimately helped make WinRT the failure we all know (and hate) today.
Just like it has been with ".Not Core" and other major components, trying to get the open source community to make use of this on non-Windows platforms has been _interesting_ in a lot of ways. The biggest 'interesting' is just how far they can take/use it for 'Embrace Extend Extinguish'... by way of open source!
Regardless of how else you see this, they're taking a failed idea and giving it away, more or less.
XAML, in theory, might make UI design easier. But when I looked closely at it [with respect to windows 8] I was horrified at what I saw. Reaching for the pink liquid, I decided that it would be a COMPLETE waste of time to take development in "that" direction. It seems, due to its lack of following, that other developers more or less agreed with me on that. (and yeah, UWP is NO better)
There are SO many cross-platform development tools, of which GTK and wxWidgets and Qt are probably the best option (or just use Java), that we do NOT need Micro-shaft cramming "their bloatware method" down anyone's throats.
On the other hand, the open-source-ness is STILL a good thing. It can provide some nice sample code on how to implement specific features that you might want to implement in your OWN open source library.
/me points out that if it weren't for ".Not", XAML, UWP, WinRT, and "The Metro", we'd have a really really good version of Windows without the controversy. That, and the 2D FLATTY. And the slurp. And the ads. And so on.