Microsoft open-sources 86-DOS 1.00, the ancestor of Windows

The source code for 86-DOS 1.00, the OS that eventually became MS-DOS and Windows, is now available on GitHub.
XDA Developers on MSN

Microsoft open-sources MS-DOS 1.0, offering a rare look at PC history

This is a rare look at the tech giant's first operating system ...

Microsoft finally open sources DOS 1.0 - and it's so much more than the code

Want a blast from the past? Microsoft just open-sourced its very first operating system, offering a rare insight into the ...

Microsoft opens door to the past by releasing 86-DOS and PC-DOS 1.00

Antiques code show Microsoft has released the source for another of its relics. This time, it's 86-DOS 1.00 getting the open ...
Ars Technica

Microsoft open-sources infamously weird, RAM-hungry MS-DOS 4.00 release

Microsoft has open-sourced another bit of computing history this week: The company teamed up with IBM to release the source code of 1988’s MS-DOS 4.00, a version better known for its unpopularity, ...
The Verge

Microsoft has released the MS-DOS 4.0 source code.

The company worked with IBM to release a 1998 uncompiled version DOS 4.0 on Thursday, although unfortunately, this release lacks the app-switching capabilities that landed it the nickname MT-DOS.
TechSpot

Microsoft releases MS-DOS 4.0 source code and floppy images through an open-source license

TL;DR: Microsoft will likely never release the original source code of Windows into the wild, but the company is clearly interested in sharing important episodes of its software development history.
InfoQ

Microsoft and IBM Release MS-DOS 4.0’s Source Code under the MIT License

Unlock the full InfoQ experience by logging in! Stay updated with your favorite authors and topics, engage with content, and download exclusive resources. Dany Lepage discusses the architectural ...