AtheOSAtheOS is a heavily multithreaded OS, written from scratch, that supports SMP, TCP/IP, a fast GUI, and most of the useful POSIX functionality. It is released under the GPL. The project has been running for some years and has reached impressive functionality: a working system, and easy recompilation of most Unix programs with ./configure; make. While traditional in design, this system has been designed for the desktop, unlike traditional posixish OSes, and deserves attention.
The AtheOS has been apparently been discontinued and a fork called SyllableOS has been started. The Syllable team has already completed a lot of major changes that make it more useable and up-to-date.
This page is linked from: Syllable