GNU hurd

GNU Hurd is the multiserver microkernel written as part of GNU. It has been under development since 1990 by the GNU Project of the Free Software Foundation, designed as a replacement for the Unix kernel, and released as free software under the GNU General Public License. While the Linux kernel soon proved to be a more viable solution, development of GNU Hurd continued, albeit at a slow pace.

GNU Hurd consists of a set of protocols and server processes (or daemons, in Unix terminology) that run on the GNU Mach microkernel. The Hurd aims to surpass the Unix kernel in functionality, security, and stability, while remaining largely compatible with it. The GNU Project chose the multiserver microkernel for the operating system, due to perceived advantages over the traditional Unix monolithic kernel architecture, a view that had been advocated by some developers in the 1980s.

GNU[www.gnu.org]