ReactOS is a new operating system that is free and open source. It is not Linux based, but rather is based on the best design principles found in the Windows NT architecture. It is binary compatible with Windows, which means that Windows applications and drivers will run on it. I plan on using it in virtual box to run iTunes (for my podcast). Wonder how long before MicroBorg tries to shut them down?
NOTE: ReactOS 0.3.16 is still in alpha stage, meaning it is not feature-complete and is recommended only for evaluation and testing purposes.