Monday, May 28, 2012
AROS is a portable and free desktop operating system aiming at being compatible with AmigaOS 3.1, while improving on it in many areas. The source code is available under an open source license, which allows anyone to freely improve upon it.
Choices is written as an object-oriented operating system in C++.
eCos is an open source, royalty-free, real-time operating system intended for embedded applications.
FreeDOS is a free DOS-compatible operating system for IBM-PC compatible systems.
Haiku is an open source operating system currently in development designed from the ground up for desktop computing. Inspired by the Be Operating System, Haiku aims to provide users of all levels with a personal computing experience that is simple yet powerful, and void of any unnecessary complexities.
HelenOS is an open-source micro kernel-based multiserver operating system. It runs on several different CPU architectures (IA-32, x86-64, SPARC V9, IA-64, PowerPC, ARM, MIPS). HelenOS prides in portability, modularity, clean design and coding style.
JNode (Java New Operating System Design Effort) is a simple to use and install Java operating system for personal use. It runs on modern devices.
KolibriOS is an operating system for the PC, written in assembly, which is based on the source code of MenuetOS. It fits on a single floppy.
MenuetOS is an Operating System in development for the PC written entirely in 32/64 bit assembly language.
NewOS is a open source operating system with an emphasis on design and portability. It is largely implemented in C/C++, with a small amount of assembly.
ReactOS is an advanced free open source operating system providing a ground-up implementation of a M$ XP compatible operating system.
RTEMS is the Real-Time Operating System for Multiprocessor Systems.
ScaraOS is a 32bit mutiboot OS kernel for IA32 (PC/AT) systems. I wrote it to teach myself OS fundamentals and just to have a bit of fun. It already has PCI support, the beginnings of a paged memory management system, and the start of a VFS layer. It supports the basic PC/AT stuff such as timer, PIC, keyboard, floppy.
Syllable was born in July 2002 as a fork of the AtheOS operating system.
Did I miss any? Please add more in the comments.