How little you know, indeed.
NitrOS-9 (not Nitro09) was started years ago by Bill Noble, Curtis Boyle, and Wes Gale to adapt the then-Tandy version of OS-9 Level Two to the 6309. Some years later, I (Boisy Pitre) and Alan DeKok back-ported it to the 6809, and added community patches and enhancements to it.
In 2003 I contacted RadiSys about releasing the 6809 source in an effort to legitimize the project. It would have been a minor bit of work for them to find the source and release it, but they never acted on the request.
Meanwhile, NitrOS-9 has been extended to support Level 1 (64K) systems and further ported to the Dragon 64, Dragon Tano, CoCo 1 and 2, as well as the Atari 8-bitters using the Liber809 board.
NitrOS-9 is just as good -- no, BETTER than Microware's 6809 version of OS-9. The tools have been written to do cross-assembly and creation of RBF disk images, and additional technologies like DriveWire have been created to allow running NitrOS-9 on 6809 hardware very easy to do.