Do you remember Mono (.Net for Linux), MFC for Unix, Microsoft Java for starters?
I do. MS-Java still sticks in my craw to this day. Don’t get me started...
.NET has been an open standard since 2003—the Mono-Project is a nearly complete open-source .NET framework for UNIX/Linux, with the exception of Windows-specific components. (Windows Forms, OTOH, is included)
As I recall, MFC was ported only to Freescale-based Macintosh: 68k and PowerPC.
Not sure about UNIX/Linux support—the closest thing I can recall was the framework that MS used to port Internet Explorer to UNIX, which wrapped MFC: MainWin XDE...