Of those, it seems like only TinyOS would qualify (a full userland stack that you can develop from) under the same qualifications that netbsd might qualify....

To be clear, by "true os", I mean a posix runtime, preemptive multitasking with threads and processes, memory protection.

Still, cool links (I'll save that TinyOS for later this week), and I like the username.

Most 8 bit micros don't have an MMU, so you can't have memory protection or virtual memory. That's a hardware limitation.

> so you can't have memory protection

You can if you emulate all memory.... I had never considered that solution before, that was my original point :)

I think you will like NuttX [1] even more :)

[1] http://www.nuttx.org/