Visual Studio 2010, C# 4.0, and it's a WinForms app. I don't see why it couldn't be run on a Linux box with Mono, but since I've never done it (and don't really have any interest in doing so), I can't say for sure. Since it requires .Net 4.0, and Mono doesn't support .Net 4.0 (that I know of), the code would probably have to be "massaged" a bit to get it to compile/run on that platform.