FreeBSD

FreeBSD is an advanced operating system for x86 compatible (including Pentium® and Athlon™), amd64 compatible (including Opteron™, Athlon™64, and EM64T), ARM, IA-64, PowerPC, PC-98 and UltraSPARC® architectures.

Free Open Source BSD Self-Hosted

Linux-libre

Linux-libre is a GNU package that is maintained from modified versions of the Linux kernel.

Free Open Source Linux

GNU Hurd

GNU Hurd (usually referred to as the Hurd) is a computer operating system kernel designed as a replacement for Unix, released as free software under the GNU General Public License.

Free Open Source Linux