I would expect some of the IP made it into Concurrent DOS and DR DOS eventually. I know in the past when I've browsed the late-DR sources there were clear line

I would expect some of the IP made it into Concurrent DOS and DR DOS eventually. I know in the past when I've browsed the late-DR sources there were clear lines of continuity between various products in their family tree (GEMDOS, CP/M, M/PM, etc), so I suspect bits ended up in that