I don't think they have much in common. There's not much out there really similar to QNX. Maybe Minix, since it's a microkernel with good userspace POSIX support. No "real time" support though. There's FreeRTOS, but it's not terribly similar to QNX either.
Thanks! My brain seemed to think the R in Reduced Instruction Set was for real time ...whoops!
Neat project regardless.
Usable for what purpose? They're about as dissimilar as could be.