No, ReactOS is an implementation of the Win32 API, not the WinNT kernel.<p>There&#x27;s a layer of separation between WinNT and Win32 that&#x27;s basically an API.  In theory if you implemented this API, then you could run Microsoft&#x27;s Win32 subsystem on your API without Microsoft&#x27;s underlying WinNT kernel.  That Win32 layer would be Microsoft code and they&#x27;d sue the heck out of you for running it.<p>The WinNT kernel was originally designed so that Subsystems would run on top of it and those Subsystems would provide the interfaces for applications.  Originally WinNT had Win32, OS&#x2F;2 and POSIX subsystems that ran on top of it.  Over time the distinction between WinNT and Win32 erroded while the OS&#x2F;2 subsystem was canned and the POSIX one neglected.<p>Starting after Server 2003 they began to redefine the boundary between WinNT and Win32.  The primary reason was to allow for headless Servers that didn&#x27;t have the overhead of the GUI (Win32) or other unnecessary functionality like the Printer systems.