Mach is a so-called first generation microkernel. Originally developed by Carnegie Mellon University (CMU) from 1985 to 1994, which was then forked and carried from 1996 onward by GNU. It is the microkernel currently used by the Hurd.
GNU Mach is mostly shipped under a BSD/MIT license, some parts are shipped under the General Public License, either version 2, or (at your option) any later version. The Linux drivers part is shipped under the General Public License version 2, but that can be disabled easily at compile time.
Implementations
- GNU Mach
- Apple's XNU (Darwin) (non-free)
- OSF Mach