Public Domain Operating System (currently x86 and 80386 and S/370 and S/390)
FreeDOS is a free DOS-compatible operating system.
FreeDOS is a complete, free, DOS-compatible operating system that you can use to play classic DOS games, run legacy business software, or develop embedded systems. Any program that works on MS-DOS should also run on FreeDOS. It doesn’t cost anything to download and use FreeDOS. You can also share FreeDOS for others to enjoy! And you can view and edit our source code, because all FreeDOS programs are distributed under the GNU General Public License or a similar open source software license.
Micro-80 aims to simulate a Z80 homebrew computer down to the bare metal: 64K RAM, ADM-3A terminal, parallel port, serial port and...3.5" 1.44MB floppy drive?!
Reenix is a combination of the best of both worlds: DOS and *x. Based on the GNU toolkit and FreeDOS, Reenix is a stepping-stone between the two OSes and a subset of *x which will run on an 8088.
RMF-DOS is a project to create a compact, 8086-compatible, free clone of MS-DOS.
A portable BASIC in the style of Microsoft 6502 BASIC (especially the Apple ][+ variant), with influence from GW-BASIC and Atari BASIC among others, with enhanced features, written in C for portability to computers large and small.
An operating system kernel designed with simplicity, readability, and elegance in mind. No longer written from scratch, but built on "the shoulder of giants." Specifics are given in the CREDITS file starting from v0.04
Real-time, modular, microkernel-based operating system under development for i386. The first goal is to support 32-bit DOS protected mode applications made with DJGPP as well as native applications.
Perix is a MS-DOS compatible program, capable of running without an underlining OS. It is written in Turbo Pascal and Assembly. All parts of system are distributed under terms of the GNU General Public License v2.
DOS-C Kernel is an MS-DOS compatible kernel and the original FreeDOS kernel.
DOS/32 Advanced DOS Extender is a drop-in replacement for the DOS/4GW DOS Extender and compatibles. Being fast, small and flexible DOS/32A can be used in many environments, from embedded systems to DOS emulators, by both developers and end users alike.
A distribution of FreeDOS which strives for Ease-Of-Use and Stability, aiming to offer a regular release schedule, utilizing the wide range of DOS-APPS available.
An update of the Unix 32v sources to an emulation layer (like posix on win32), or a .net service (win32v.net!)
Fusion OS is a Open Source Operating System, mainly licensed under the MPL 1.1. Parts of it are licensed upder the GNU GPL or other open source licenses. Fusion OS is based on the ReactOS project, and we contribute any bugs found in ReactOS back to them
The Omicron OS Kernel Project, is a another attempt to create an open source operating system. However one fundamental difference between this OS and the others is that, the omicron project will have user useability taken into account right from the begin