C# is much better these days about cross platform compatibility and open source. It's only going to get better too from what I can tell from observing Microsoft's path thus far. They've changed their strategy a lot.

Check this out: http://techcrunch.com/2015/04/29/microsoft-shocks-the-world-with-visual-studio-code-a-free-code-editor-for-os-x-linux-and-windows/