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
Imagine the possibilities.

An operating system usable by virtually every still-functioning computer in existance today, and a horde of programmers who can work in such a simplified environment that can write virtually any program for any task needed.

Who can write me a DOS 4 web server?

@starraven @shanselman Sioux should work, though you might need the network layer (maybe the one from freeDos could work) http://www.georgpotthast.de/sioux/
SIOUX - A Web Server for DOS

DosUHCI is a new USB host controller driver to support USB device drivers for DOS