AOS is because A is better than any other D, uC, etc OSes :).
It uses yagarto compiller distribution for ARMs.
It can run on LPC23xx microcontroller:
- has its own memory management
- stdio is redirected to the SCI device
There are few modules under GNU/GPL licence taken from another projects.
C++ exeptions are not supported now, but it is possible to have C++ execeptions on ARM7 embbeded system (hack into C runtime lib to switch execption context is required).