Technology choices
_delirium: Open-source developers often want to develop on Linux, or at least to be able to release cross-platform stuff that will work on Linux, and Microsoft's toolchain is generally not oriented in that direction. If you use their dev tools, you're usually just building a Windows .exe, and if you want to port, it's going to be extra effort. There are of course Windows-only open-source projects, and they do actually often use an MS dev toolchain.I think if Microsoft had (especially earlier on) been somewhat friendlier with the cross-platformness of .NET, either with their own releases or by helping Mono be a more compatible option, it would have more uptake, because technically it's actually pretty nice.