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DR-DOS rises again – rebuilt from scratch, not open source

Project claims legal clarity and zero legacy code, but offers binaries only DR-DOS is back, and there is already a test ...

DR-DOS is coming back from the dead, rebuilt from scratch in pure assembly

A one-man company named Whitehorn Ltd. Co. recently announced that DR-DOS is coming back. The "new" text-based operating ...
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, ...
Liliputing

Microsoft releases source code for MS-DOS 4.0 (and Multitasking DOS)

A decade after releasing the source code for MS-DOS 1.1 and MS-DOS 2.0, Microsoft has open sourced a (slightly) more recent operating system: MS-DOS 4.0. First released in 1988, you can now download ...
Ars Technica

Microsoft and IBM release source code for one of the weirdest versions of MS-DOS

That screenshot seems to be MS-DOS 5.0 or later. How many end users had hard drives when 4.0 was released? Click to expand... We had a 20MB hard drive in a PC-XT clone made by Sanyo which was running ...
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.