Fiasco.OC-UX
Fiasco.OC-UX is a port of the Fiasco.OC microkernel to the Linux system-call interface. Due to its special design, it runs without kernel-level privileges, despite the fact that it is a fully functional L4 microkernel. Because it uses GNU/Linux as host system, it can run on any x86-based system as a normal user-mode application.