Syllable Desktop is a complete operating system that is easy to use, powerful, lightweight and extraordinarily fast and responsive. It has its own kernel, filesystem, GUI and applications. Syllable Server is a matching small and efficient Linux server.
Haiku is an open-source operating system currently in development designed from the ground up for desktop computing.
"µOS++" (micro OS plus plus) is an open source, royalty-free, real-time operating system intended for embedded systems built around ARM Cortex M or AVR devices. It is based on a preemptive scheduler written in C++ (more info in the Wiki).
FreeOS/1 is a Free, Open Source, FreeDOS based Free and Open Source Alternative OS, with open source Microsoft Windows compatibility using HXDOSExtender KernelEx,and ReactOS source code. FreeOS/1 will include new technologies and will be easy to use
An open source operating system for x86.
A fork of ReactOS which aims to be compatible to the NT architecture (but not a clone) meeting WINE's standards every time a part of NT interface is implemented. The fork was done at revision 9494 before ReactOS changed slowly into Tinykrnl.
Acquaintance OS aims to be a lightweight Linux distribution based off of OpenSUSE. Remember, don't be fooled by the OpenSUSE branding, this project is very different from OpenSUSE, software-wise and goal-wise.
Jinx is a minimalistic graphical operating system for use on old computers with 64MB RAM. Suitable for desktop,business,library use. Includes browser, office applications in 50MB ISO. Optimized for tiny size.
Next generation Linux Operating System for the enterprise and public. Reliable solutions for the internet, datacenter, security, office and entertainement.
A little operative system with File System, Process Manager, but without a Grafical User Interface :'(
CJet eXTreme OS is a new project to develop a cross platform operating system with a native application interface designed to make it easy to develop for several architectures at once.
The CK 64-Bit Kernel Operating System
This project is a implementation of layers. Use Virtual machines & virtual adapters alike an onion! Another operating solution instead of Microsoft Windows Server operating system. It is to be used via remote controlling. The special new "Cktool32" will make it easy to handle *Ck64Krnl*.
An open-source alternative to Apple Mac OS X. Intended to comply completely with the OPENSTEP specification. Written in Objective-C. Kernel based on FreeBSD.
Cellocity Linux is Based on Fedora Core 6 Source Code. With only basic core elements needed to operate Compatipal and a completley Graphic Interface as well as Text. Version 2.0 will include more applications 32,64 bit and 80 Core Intel CPU
It is a Uruguayan Linux distribution. Can be used from floppy disks, cdroom or you can install it in your hard disk. It has been designed to be fast and effective without leaving of side the graphical aspect for the user.
An Open-Source OS project aiming on simplicity and being lightweight
An OS aiming on community-developed OS.
New Linux Based OS primarily for smart devices and PDA's, laptops, and eventually desktops. It offers an alternative to the "embedded" approach. All OS versions and applications will be hosted and then made available to the subscribers of cloud svs
Embedded Operating System
EXIRION/OS is an operating system for embedded computer systems. These operating systems are designed to be compact, efficient at resource usage, and reliable, forsaking many functions that non-embedded computer operating systems provide, and which may not be used by the specialized applications they run. They are frequently also referred to as real-time operating systems, and the term RTOS is often used as a synonym for embedded operating system. EXIRION/OS project, a Open operating system for computers that can be used in specific operations that require execute a task at a time, EXIRION/OS operating system is a monolithic and mono layered task, which can be used to control complex electronic equipment without the use of instruments PLC, offering a wide range of electronic and industrial applications, EXIRION/OS is also an educational tool, it is an open source operating system to use it as an example of building operating systems in universities and technical colleges.
Linux-based x86 operating system designed to run in an educational environment.
FIRNix is a collaborative effort between students and professors of FIR to develop in C/C++ a robust, full-featured and Open Source out-of-the- box Unix-like Operation System based initially on Minix and progressively improve your functionality."
FOS - open source 32-bit microkernel operating system.
A special-purpose 4.4BSD-based UNIX-like operating system, designed for machine control applications. Using low-cost hardware, FabBSD can be used to control a wide array of CNC milling machines, lathes, routers, process-control and automation equipment.