This project is quite interesting, and very promising, if it's actually available. RTEMS is an very well-characterized RTOS originally designed by the military (a Real Time Executive for Missile Systems was the original meaning), and it conveniently has a POSIX layer. I've built some things out of RTEMS and found it to be a pretty enjoyable experience, once you get a build environment set up (and don't touch it when you do!).

I have to wonder though, has Peer actually released any code yet? I implored him to release a couple of years ago, and wasn't successful in convincing him. At the time, he was insisting on some drivers to exist before he'd be willing to. I was quite disappointed.