Aero is a new modern, experimental, UNIX-like operating system following the monolithic kernel design. Supporting modern PC features such as long mode, 5-level paging, and SMP (multicore), to name ...
Guix is an advanced distribution of the GNU operating system. Guix is technology that respects the freedom of computer users. You are free to run the system for any purpose, study how it works, improve it, and share it with the whole world.
AtheOS is an GPL'ed alternative OS running on Intel based PC's. Featuring an object oriented GUI interface, multi threading SMP, journaling filesystem, TCP/IP network stack and various other components expected in a modern desktop OS