That doesn't apply here. This is a strategic purchase for Microsoft. They have no competing technology. That was in reference to standards. Microsoft wanted to turn open standards into proprietary standards to drive people toward their products.
That's all I know that Xamarin makes, so I think this article is going a bit over my head, but it'll be a shame if I suddenly need a Microsoft account to use it. I do like diversity in my language tooling.
Xamarin Studio is a swiss army knife. I don't know about your use case, but I use it under the name Monodevelop on linux (not really sure what that association is) and as Xamarin studio on windows. For my use case, it's a C# and C++ IDE for desktop development, same as visual studio.
It's certainly not a MacOS only product, it supports all three platforms including windows.
Mono only supports a subset of the whole stack.
No sane .NET developer would use Mono on Windows, its purpose is .NET portability to other OSes.
WHY ARE WE ARGUING?
explodes
Poor guy. His name autocorrects to one of the best-known names in computing.
Last I checked, that was just a forked and rebranded Mono Develop with Xamarin's main product line (iOS and Android support for .NET) bundled in.