The OS List is a list of operating systems, both proprietary and open source (or free). The list is far from complete and probably never will be as there are tons and tons of small OS projects popping up all the time. I will try and post the more "interesting" ones.
Proprietary
AmigaOS - It is the default native operating system of the Amiga personal computer. It was developed first by Commodore International, and initially introduced in 1985 with the Amiga 1000. It ran on the Motorola 68k series of 32-bit microprocessors, except for AmigaOS 4 which runs on PowerPC microprocessors.
Athene - Athene is a commercial operating system developed by Rocklyte Systems for use in the home and office. Athene combines years of Rocklyte's R&D with the latest Linux technology to create one of the fastest operating systems available today. With boot times as fast as five seconds and advanced graphics technology not available in standard Linux distributions, Athene is the best low-cost alternative to Windows for your computer desktop.
BeOS - BeOS is an operating system for personal computers which began development by Be Inc. in 1991. It was first written to run on BeBox hardware. Unlike some other operating systems of the time, BeOS was written to take advantage of modern hardware.
eComStation : eCS is what has become of the once famous IBM OS/2 operating system. It is currently 100% OS/2 compatible. Version 2.0 is currently in RC3 stage (release canditate). There are plans on one more RC version before the final version is released.
MAC OS - Mac OS is the trademarked name for a series of graphical user interface-based operating systems developed by Apple Inc. (formerly Apple Computer, Inc.) for their Macintosh line of computer systems. The Macintosh user experience is credited with popularizing the graphical user interface. The original form of what Apple would later name the "Mac OS" was the integral and unnamed system software first introduced in 1984 with the original Macintosh, usually referred to simply as the System software.
Microsoft Windows : Need I say more?
OS/2 - OS/2 is a computer operating system, initially created by Microsoft and IBM, then later developed by IBM exclusively. The name stands for "Operating System/2," because it was introduced as the preferred operating system for IBM's "Personal System/2 (PS/2)" line of second-generation Personal Computers. OS/2 is no longer marketed by IBM, and IBM standard support for OS/2 was discontinued on December 31, 2006. Currently, Serenity Systems sells OS/2 under the brand name eComStation. Wikipedia Entry.
RISC OS - Is the superbly efficient operating system designed in the 1980's by Acorn Computers, and its latest incarnation is used by thousands of people around the world. Pre-dating both Windows and Mac OS to use a task bar or 'Dock', RISC OS includes many revolutionary features which are only just being copied by other systems. Its anti-aliased font technology is still the envy of the computer world and its drag 'n' drop, stackable windows GUI, flexibility and ease of use make it arguably the most productive computer system in the world today. More at http://www.riscos.org.
SkyOS - The Sky Operating System, or SkyOS, is an operating system written for x86-based personal computers. SkyOS was created in 1996 by Robert Szeleney as a small bootloader. In the past 8 years, SkyOS has evolved into a full-featured, modern operating system, with a goal to be the easiest to use desktop operating system available for the average computer user. The development staff has also increased to include business, software, and graphics developers. As of SkyOS 5.0, SkyOS will be a commercial operating system.
Unix - (officially trademarked as UNIX®) is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs including Ken Thompson, Dennis Ritchie and Douglas McIlroy. Today's Unix systems are split into various branches, developed over time by AT&T as well as various commercial vendors and non-profit organizations.
Zeta : Zeta is an proprietary reincarnation of BeOS originally developed by YellowTAB and then by magnussoft . Due to legal problems it is now shut down and doesn't look like it will come back anytime soon.
Open Source and/or Free
AROS (Amiga Research Operating System) - The AROS Research Operating System is a lightweight, efficient and flexible desktop operating system, designed to help you make the most of your computer. It's an independent, portable and free project, aiming at being compatible with AmigaOS 3.1 at the API level (like Wine, unlike UAE), 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.
BlueIllusion OS - BlueIllusion is a micro kernel based operating system, which operates on the Intel X86 Architecture. It uses some features like paging to some excess to get work done. Other things like TSS-based Hardware task switching aren´t used. It will - in the future - have a graphical user environment, which I intend to be analogous to the MAC OS 9 GUI, with a Menu bar that appears when moving the mouse to the upper border of the screen - as well as support for a right-click-popup menu under the mouse at needs.
Cosmoe - Cosmoe is a new user interface that runs on top of the Linux operating system (and soon others). Cosmoe implements a powerful but easy-to-use high-level C++ API that is quite similar to BeOS. In fact, many BeOS programs can be recompiled to run on Cosmoe with little or no changes!
Cosmos - Cosmos (C# Open Source Managed Operating System) is an operating system project implemented completely in CIL compliant languages. The team is committed to using C#, however any .NET language is usable.
Cosmoe is not a polished, completed work yet. Most of the current work is going on "under the hood", so we don't have a lot of flashy graphics to lure you in. However, Cosmoe does have a very solid foundation, and we look forward to the involvement of the developer community in helping Cosmoe to mature.
FreeDOS - A free MS-DOS clone.
GeekOS - GeekOS is a tiny operating system kernel for x86 PCs. Its main purpose is to serve as a simple but realistic example of an OS kernel running on real hardware. (Actually, most of the development is done on the Bochs emulator.)
The goal of GeekOS is to be a tool for learning about operating system kernels. As of version 0.2.0, it comes with a set of projects suitable for use in an undergraduate operating systems course, or for self-directed learning. GeekOS has been used in courses at a number of colleges and universities.
Haiku : 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 - The HelenOS project is an effort to develop a complete and usable modern operating system, yet offering room for experimenting and research. HelenOS uses its own microkernel written from scratch and supports SMP, multitasking and multithreading on both 32-bit and 64-bit, little-endian and big-endian processor architectures, among wich are AMD64/EM64T (x86-64), ARM, IA-32, IA-64 (Itanium), 32-bit MIPS, 32-bit PowerPC, SPARC V9 and Xen 3.0. Thanks to the relatively high number of supported architectures and suitable design, HelenOS is extremely-well portable.
JNode - Java New Operating System Design Effort. JNode is a simple to use & install Java operating system for personal use. It runs on modern devices. Any java application will run on it, fast & secure!
KolibriOS - KolobriOS is an open source operating system with a monolithic preemptive kernel, video drivers, for 32-bit x86 architecture computers, developed and maintained by The KolibriOS Project Team. KolibriOS is a fork of MenuetOS , written entirely in FASM (assembly language).
Linux : Here is the definition from Wikipedia - "Linux (IPA pronunciation: /ˈlɪnʊks/) is a Unix-like computer operating system. Linux is one of the most prominent examples of free software and open source development; its underlying source code can be modified, used, and redistributed by anyone, freely."
MenuetOS - MenuetOS is an Operating System in development for the PC written entirely in 32/64 bit assembly language, and released under the License . It supports 32/64 bit x86 assembly programming for smaller, faster and less resource hungry applications.
MikeOS - MikeOS is a 16-bit operating system for x86 PCs, written in assembly language, which boots from a floppy disk or CD-ROM. It features a text-based dialog-driven user interface, a command-line, support for FAT12 (DOS) floppies and PC speaker sound. It can load external programs and has over 30 system calls. Basic DOS .COM program support is also included.
osFree - osFree is a open source free (non-commercial) software development project. Goals of the projects are to replace all (or most) of OS/2's subsystems with open-source analogues. The base compatibility system is OS/2 Warp 4 (Merlin), but that doesn't mean we won't be supporting features of newer versions of OS/2 like OS/2 WarpServer for e-business and eComStation by Serenity Systems.
Plan 9 from Bell Labs - Plan 9 from Bell Labs is a distributed operating system, primarily used as a research vehicle. It was developed as the research successor to Unix by the Computing Sciences Research Center at Bell Labs between the mid-1980s and 2002. Plan 9 is most notable for representing all system interfaces, including those required for networking and the user-interface, through the filesystem rather than specialized interfaces. Plan 9 aims to provide users with a workstation-independent working environment through the use of the 9P protocols. Plan 9 continues to be used and developed in some circles as a research operating system and by hobbyists.
ReactOS - The ReactOS® project is dedicated to making Free Software available to everyone by providing a ground-up implementation of a Microsoft Windows® XP compatible operating system. ReactOS aims to achieve complete binary compatibility with both applications and device drivers meant for NT and XP operating systems, by using a similar architecture and providing a complete and equivalent public interface.
Syllable - The goal of Syllable is to create a reliable and easy-to-use open source operating system for the home and small office user. We also want to encourage developers to create an operating system that is intuitive, easy to use, and powerful.
Visopsys - An alternative operating system for PC compatible computers. Under development since late 1997, this system is small, fast, and open source. It features a simple but functional graphical interface, real preemptive multitasking, and virtual memory. Though it attempts to be compatible in a number of ways, Visopsys is not a clone of any other operating system. You can demo the distribution from a "live" CD or floppy disk.
Web Based
eyeOS - A completely free (Open Source) Web Operating System running from your browser, where anybody can collaborate and expand it.
YouOS - YouOS is a web operating system that lets you run diverse applications within a web browser. Small applications like sticky notes or clocks. Large applications like word processing, mp3 players, and instant messaging. Even better, it's very easy to tweak an existing application or write your own.
ajaxWindows - a complete virtual PC you can experience using only a browser from any web connected computer.
eyeOS - eyeOS is a new kind of Operating System, where everything resides on a web browser. With eyeOS, you will have have your desktop, applications and files always with you, from your home, your college, your office or your neightboor's house. Just open a web browser, connect to your eyeOS System and access your personal desktop and all your stuff just like you left it last time.
