"Among the many free software projects out there, I think ReactOS is particularly worth some discussion. This is an effort to create a complete, clean room re-implementation of the entire Microsoft Windows NT operating system. Here is why I think this project is important:
"First, we do have lots of free software today that is either written for, or has been ported to, Microsoft Windows. For those who wish to write such software, or to create portable applications that they may wish to later migrate to other platforms, it is essential to be able to target a clean and generic reference implementation of the Microsoft framework, freed from secret and undocumented behaviors..."
