Sometimes in life you make bad choices and the DR-DOS guy made the worst mistake of his life...
The story went like this...
IBM needed an OS for the PC and they went to meet the guy of DR-DOS.
DR-DOS guy instead of meeting with them said something like "I'd rather go fly my airplane"
during those days you wouldn't piss off IBM folks, like the saying nowadays go "You can't go wrong if you use M$ products" it was same back in those days, except it was IBM that was ruling with a IRON FIST!
Then IBM went to M$. The rest is history.