Blazingly Fast & Customizable Linux distribution
Real-Time Event Frameworks based on active objects & state machines
Just bring Linux for a better world
Free real-time operating system designed for microcontrollers
LuninuxOS is a Debian/Ubuntu based Linux distribution.
Auto-Case converts your mistake into perfection!
Open-source RTOS and Embedded Systems Toolkit for C++ and C
SuperWikia: The Runtime/Realtime Environment for Codesmiths
Universal Operating System
PrimOS is a 32bit multi-task OS, which is still under development.