> DR was still planning DOS

No, DR was planning CP/M-86.

I feel like I'm going down this thread posting corrections, but when trying to thrash out the details, I think it's vital to get the details right.

DR was about 3Y late with CP/M-86. The 8086 shipped in 1979, IIRC -- I was only 12 -- and there was no CP/M yet. The IBM PC shipped in 1981. Still no CP/M.

Tim Paterson, author of QDOS, went on record as saying he'd never have bothered if CP/M-86 had actually shipped.