NitrOS-9 is a multi-task operating system for the Dragon and CoCo computers. It was originally based on OS-9 from Microware as an optimized version for the 6309 microprocessor. Over time it turned into a open-source project and is still under development. NitrOS-9 Level 1 is similar to OS-9 Level 1 and can run on the Dragon 64. It can actually boot on a Dragon 32 as well, but with very little RAM left to do anything useful. NitrOS-9 Level 2 is similar to OS-9 Level 2 and requires the GIME memory management unit (MMU) and extra memory of the CoCo3.
NitrOS-9 has support for the Dragon Data disk controller (thanks to Phill) and for DriveWire.
Visit the NitrOS-9 project for more information.