This is from October 2018.

Microsoft liberates ancient MS-DOS source from the museum...
As Microsoft gears up to unleash the Windows 10 October 2018 Update, Rich Turner, guardian of the command line at Redmond, took a moment to remind us of simpler, MS-DOS-based times.
After original author Tim Paterson found the source for MS-DOS 1.25 (along with a six-inch stack of assembly print-outs), Microsoft handed the code for 1.25 and 2.0 to the Computer History Museum back in 2014.
Nice to know.
And it is available elsewhere as a ISO for a bookable CD!
https://superuser.com/questions/1230464/how-do-i-create-a-custom-bootable-ms-dos-iso-image.
In the link above the user had some issue with it.
But it works for me.
Microsoft ain't crazy, they are releasing something obsolete. Even MS-DOS 2.0 is limited compared to later versions. Support up to 16 MB or 32 MB FAT12 formatted hard disk drives depending on the formatting tool shipped by OEMs, and 5.25-inch, 180 KB and 360 KB floppy disks. Version 3.30 was the first version I ever used. Supports 3.5-inch, 1.44 MB floppy drives and diskettes, extended and logical partitions. I had an Epson Equity II PC-XT clone with a 40 MB hard drive and a CGA adapter. I later got a Hercules card and a compatible monitor in exchange for a moped that didn't run. Happy days. I then pirated MS-DOS 6.22 from a friend's machine by copying everything ONTO a stack of floppies over about a week.This first link I gave mentions GitHub.
Here is some info about GitHub mad why it matters to software developers.
https://www.economist.com/the-economist-explains/2018/06/18/what-is-github
Published in The Economist , Jun 18th 201.
Quote

STEVE BALLMER, Microsoft’s former chief executive, became an internet meme when he gave a speech to employees in which he bounced across the stage shouting “developers” over a dozen times. While much has changed since Mr Ballmer’s chant, developers remain central to Microsoft’s strategy. Earlier this month his successor, Satya Nadella, announced that Microsoft would acquire GitHub, a platform for hosting software code—especially “open-source” projects—for $7.5bn. Developers took to the internet in outrage, predicting a slow death for the service. Many non-coders, meanwhile, were left wondering what all the fuss was about. What is GitHub, and why do developers care so much about it?

GitHub is designed around Git, a system for tracking changes in software code. Git was originally created by Linus Torvalds, a Finnish-American software engineer, to track changes in Linux, an open-source rival to Windows that he designed. Unlike the previous generation of version-control software, Git was designed to track software written by a large, disparate group, rather than by a managed team at a software company. It allows multiple developers to work on the same code in different places, and to integrate their changes later. But WHEREAS Git makes such collaboration possible, it hardly makes it easy. To work out just what another developer has changed requires users to enter ARCANE directives at a command prompt and scroll through pages of text

I later got a Hercules card and a compatible monitor in exchange for a moped that didn't run.