See Hurd about the expansion of the "Hurd" acronym.

What is the GNU Hurd?

The GNU Hurd is the GNU project's replacement for the Unix Kernel. The Hurd is a collection of servers that run on the Mach microkernel to implement file systems, network protocols, file access control, and other features that are implemented by the Unix kernel or similar kernels (such as Linux).

Check out the Hurd wiki at http://hurd.gnufans.org/bin/view/Hurd/WebHome or the main page at http://hurd.gnu.org

Each server in Hurd is only assigned the permissions it needs to do its job; and each server runs independently in user mode. This differs from monolithic kernel designs such as Linux, where all of the code runs in kernel space as a superuser.

Hurd allows drivers to run as a user; and can even allow users to load up their own servers without rebooting or affecting the stability of other servers or other users on the system or having to get superuser privileges to do so.

Quote: "In short: just say NO TO DRUGS, and maybe you won't end up like the Hurd people." -- LinusTorvalds

(Amusing; but possibly not entirely appropriate --SamDouglas?)