We have a large application that runs under QNX4 on an x86 board and I'm looking for a way to propose a replacement. The decision has already been made to not upgrade to the latest QNX.

What I'm thinking of is some GPL/BSD/MIT licensed OS that could be enhanced to allow our product to compile and run almost unmodified.

Specifically, I need independent processes (not just tasks), network, filesystem (that ideally could access the existing QNX filesystem), /dev/mqueue/ for interprocess communications and a shell (no graphics). We don't strictly need a realtime OS, as long as performance is good.

Is this big and daunting, or is there something that almost fits?

Any suggestions?