The Microsoft C standard library implementation also takes this approach - C++ implementation with C exports, for the reasons called out by the sibling comments.
Interestingly enough, it wasn't $future_version, but version 1.0, that didn't even support .NET and was scriptable only through JS. Silverlight is still scriptable through JS to this day. Given that Silverlight already supports a hybrid model I can image we could expect that to continue, with HTML as a possible alternative UI langauge to XAML.
FolderShare was acquired. I don't know if Microsoft has done a terrible lot with the program since the acquisition to be able to claim the success as its own.