It is a bit of a stretch to say that FreeNAS is based on monowall. I believe that it is really just the php Web interface and documentation that is based on monowall, not necessarily the underlying architecture.
Sounds like: This webinterface is cool and will fit to freenas, let us take this. We use freebsd, too, so we can say it is based on... right?
Anyway, i will try m0n0 beta as test.