Yesterday's MINIX post made me remember the Freedows OS project; I talked about it with a friend recently, who didn't know about its existence, so hence this post.
Freedows was an operating system that aimed at providing multi-platform emulation. It was born in 1996 and was based on a microkernel architecture. It had to have servers for different popular operating systems, such as Windows, Linux and DOS (IIRC), allowing the user to run applications from each of these seamlessly.
It is a pity that it was abandoned in 2002, possibly because its high ambitions and expectations. It seemed to be quite popular at its time, as I recall articles about it in generic computer magazines. What is worse, the web site disappeared together with the code (I guess it is still somewhere else for historical reasons, though). Check out the Wikipedia article for more details.
Fortunately, we now have ReactOS, which is coming along nicely and also plans to incorporate non-Windows subsystems.
BTW, a quick Google search shows a Linux distribution from Brazil whose name is Freedows. Don't get confused, as it is completely unrelated.