> MS has realized that their power in the tech industry is not dependent on their source code being a secret, and that in fact making your stuff open source makes you more popular and influential.

It has been a huge boon for .NET as well. Serious contributions started pouring in almost immediately. Code from Mono being ported over; linux support. Fixes to really old issues that were not getting attention because .NET was essentially put "in a box".

C#, .NET and the CLR are pretty great tech that could have been a true Java alternative if not for the fact the vision for it was so narrowly scoped to Windows.