Ralph Gerlich's Knewcleus is a microkernel-based real-time OS that aims for POSIX compliance; while open sourced, the people behind it intend to make it a commercial venture and release a packaged version that will include additional things not present in the opensource version. Latest news date back to jan 2002, stating that a first version would be ready by mar 2002, so it should be considered MIA. There was documentation and CVS code on the former site, but almost nothing on the current one.