The original open source?
At the time of these events, I owned a Xerox 820 (a Z-80 based machine) and soon thereafter a Kaypro (pretty much the same thing in a nice box - the 820's we got as bare boards, surplus). At my job for a "beltway bandit" we'd been doing embedded work for various parts of the US government, and were embedding Z-80 and other similar things, and had an Intel Dev system (insanely overpriced but it was gov money).
I had the source code for CP/M (a friend in the government...) and basically used that as documentation for the Intel DOS system. We had phone support on that Intel system and even spoke with Gary Kildall a few times - nudging him (without success) to look into our interrupt driven and in most cases re-entrant system hardware drivers, developed for our customers, as they would have made the Intel system a lot better. He didn't go there - Gary was Gary and it seemed, working well below what should have been his pay grade, soon to leave Intel. He didn't think it worth the effort and frankly, that class of ideas was pretty blue-sky given the capabilities of the existing hardware.
At the time we didn't think much about how similar the opsys were - and it wasn't just the int 21 calls that were identical - int 10h also - the bios...that entire concept. We were super enthused about having actual disk drives (FAT 12!) - remember that back then people were fiddling with dodgy cassette things, or were old school users of restored/surplus PDP-8's and teletypes/paper tape. BYTE magazine hadn't started up yet, quite. Everything we saw, or nearly, was following the obvious trend of filling some utterly obvious need - adding storage - there's never enough memory - adding I/O and so on, and any framework that helped make that happen was welcome. Whatever-you-call that opsys (CP/M, DOS) didn't matter, and it didn't seem weird that they were really all the same thing inside - not just the api (glad Oracle wasn't around!) but the bits, the source, same stuff. There were only so many ways to skin a cat when every byte (all semiconductor ram was static then, as god intended) and clock tick seriously mattered.
MS claim to fame then - and make no mistake, they weren't bad guys then - was the very best tools to program the little 8 bit guys - M80 and L80. Nothing else out there "just worked".
There plain wasn't enough of this stuff around, or adoption of what there was for other than hobby use (and some avionics and other things my outfit built) for us to even think of IP issues (which weren't named at all then) or the fact that this would snowball into a huge effect on the world with attendant redistribution of $$$. That was the thing Gates got right....not necessarily in a pleasing way.
Similar to Jobs real main contribution was getting the **AA's to partly remove their crania from their anus and make digital sales of some content legal. In both cases the rest simply followed.
Over the years I pointed out the similarity or near identical nature of MS-DOS to CPM and Kildall's dev system only to receive scorn and "no way, it couldn't have been " and even saw wikipedia articles explaining parallel development and that this wasn't just copied from Kildall's work.
All I wish is that A: he'd listened to us and created the basis for real multitasking as a result, and B: Microsoft's blatant copying would have resulted in a lot better initial windows instead of how things did go. But Gary was Gary - from a little bit of contact as a customer, I tend to believe the tales of his "loose cannon" exploits. He was a real character.
Pretty sure no one really wants to hear possibly misremembered history from one who was THERE, so I'll just get that coat now. We'll all miss the guys who made this all go, and in my case created the chance at a really good and long career in the biz.