NilRTOS - A Fast Tiny Preemptive RTOS

Not sure if I ought to be starting a new thread, rather than continue with this old one - but here goes!

NilRTOS looks promising for my project. I've got it more or less working with SCoopME, but want to see if NilRTOS is better suited, and more compact.

I've noted in all the examples the warning:

"Loop is the idle thread. The idle thread must not invoke any kernel primitive able to change its state to not runnable"

I'm not sure what this means and its implications for my project! My existing code has functions that access an LCD, and functions accessing a few digital sensors.

What sort of functions do I need to look out for, please?

Jim