Do you still long to run WordPerfect 5.1, Lotus 1-2-3 4, or Doom on DOS? Well, if you do, there's a new way to revisit the PC world of the 1980s: The newly open-sourced PC-MOS/386 v501.
PC-MOS, for those who weren't around in 1987, was a multi-user MS-DOS clone by Norcross, GA's The Software Link. It ran most standard DOS and 386's protected mode applications. I reviewed it back in the day -- although I can't find my article from Computer Digest, a Washington DC regional general interest computer newspaper, I recall it worked well.
Much to everyone's surprise it turned out that Roeland Jansen, one of its developers, still had PC-MOS's source code on tape. He was able to get permission from the other intellectual property owners to release the operating system in July and now an archaic operating system lives again.
This release is of the last commercial version. It includes both the x386 assembler and C source code, the executables, and a bootable 3.5" floppy disk image. It also comes with a CD-ROM driver. The PC-MOS/386/The Software Link inc/CDROM code, however, is not open-sourced.
The suggested way to run the operating system is to use Unix/Linux's dd command to create a bootable image from the floppy disk image. Then, you can run it on VMWare Workstation or Oracle VirtualBox. If you have a working PC from the 80s, you can also, of course, try it by using a physical 3.5" floppy drive.
The newly released code is under the General Public License (GPL) version 3 open-source license. It includes all the sources needed to build PC-MOS386 v5.01. patch level 6.
To compile and link the code, you'll need 1992's Borland C++ 3.1 compiler. Other compilers may work. It's not clear if the Borland compiler was ever released to public domain, but this archaic compiler is widely-available for download.
So, if you want to revisit the good old days of MS-DOS computing and programming, have fun!