We just open-sourced DOS 4 (and found binaries of Multitasking DOS 4) https://www.hanselman.com/blog/open-sourcing-dos-4
Open Sourcing DOS 4

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@shanselman Wow! Any plans to open source Windows 3.1 or any of the Windows NT line?
@tharkys @shanselman Windows 11 is Windows NT, so I suspect that even Windows NT 3.5 code would still be somewhat relevant today, so I would be surprised if they release it. However, I wouldn’t be as shocked about open sourcing it today than I would have been 10 years ago…