Both are probably too entangled with Windows internals. Windows Forms is essentially a wrapper around native GDI controls. WPF's rendering system is quite intertwined with the DWM

It's much easier to open-source the things with fewer dependencies, such as .NET Core, ASP.NET and other networking stuff. It's also invariably what customers are likely to want to run on Azure (or elsewhere), just maybe not with Windows underneath it.

For WPF I'm content with MS actually continuing development. WPF is the best UI framework I've used so far with a lot of good ideas that have sadly been ignored by most others. It's just sad that it got so little attention in recent years.

I use WPF everyday and it has many great features. But sadly it was conceptualized before many of the 'modern' and best features of .net. The striking lack of type support (generics), and frankly broken separation between form and function, makes it feel very clunky at times. Not to mention that while data-binding is first class, the predominant MVVM pattern is sadly bolted on. My last gripe is that in most WPF applications, the only reason the application hangs is due to rendering performance - which is truly unacceptable given every other part of my application can be multi-threaded or async.

Entirely true. Still, seems like if they were to open-source WPF, the Mono community would have an interest in trying to abstract out the DirectX dependencies and making it run on OpenGL. Shame we'll probably never see it happen - it would be great to see a true cross-platform GUI toolkit for .NET that's not GTK.

That's the line so far...who knows about the future...

During the talk at Build on WPF there were some slight hints that it may be open sourced at some point in the future, I'm not holding my breath though.