Free-DOS Project [IA][Direct] -
The goal of Free-DOS is to create a free MS-DOS compatible operating system. Much work has been completed, but there is still a lot to be done.
Mike Podanoffsky's DOS Page [TheOldNet][Direct] -
Contains code for RxDOS - full MSDOS compatible. Also contains RTX, a very small, very fast real-time kernel. Is home to the upcoming Vivaldi real-time virtual operating system.
PTS-DOS [TheOldNet][Direct] -
Operation system, fully compatible with MS-DOS developed by the russian company PhysTechSoft.
SuperDOS [TheOldNet][Direct] -
A multi-user operating system running on industry-standard Intel hardware.