I'm not 100% either, but IIRC there were different groups working with C# back in the day. Microsoft was the largest, but least open. I think Xamarin was one of

I'm not 100% either, but IIRC there were different groups working with C# back in the day. Microsoft was the largest, but least open. I think Xamarin was one of the large open groups that was developing for/with C#. The .NET foundation was supposed to make C# a vendor and platform agnostic language from what I understand, giving Microsoft and others like Xamarin a seat at the table.