They've had problems in the past, based on the legitimacy of reverse engineering Windows: https://en.wikipedia.org/wiki/ReactOS#Internal_audit https://en.wikipe

They've had problems in the past, based on the legitimacy of reverse engineering Windows: https://en.wikipedia.org/wiki/ReactOS#Internal_audit https://en.wikipedia.org/wiki/ReactOS#Internal_audit > Even if they abandon the project it's open source and work can continue even after MS has their way with them. Such infringement claims are damaging to the legitimacy of the codebase itself. Anyone taking up the project could face the same problems.