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
Bah, 3.3 was the best vintage :)
@ian
That's *why* they've skipped that version - it's (presumably) still being used!
@shanselman