We can't help with this RTOS, however; you should focus on something that has open standards so you aren't locked in. The Linux/POSIX community is the most common standard although not the only one.
For m16c try: http://rowebots.com/Embedded_Processor_support/renesas_m16c_development
General info:
http://rowebots.com/products/dspnano or http://rowebots.com/products/unison
Using these open standards and off the shelf I/O support with a tiny tiny Linux compatible rtos will get you the best solution overall and the development is FREE, the source code is FREE and non commercial development is FREE.
Kim