ReactOS: Open Source Microsoft Windows®

ReactOS is an Open Source effort to develop a quality operating system that is compatible with applications and drivers written for the Microsoft Windows NT family (Windows NT, Windows 2000, Windows XP) of operating systems. ReactOS is licensed under the GNU General Public License (GPL).
Before ReactOS Around about 1996 some people formed a group called FreeWin95, with the goal to implement an operating system that would be a clone of Windows 95. Unfortunately, as with many new ambitious Open Source projects, it was stuck in a rut of endless talk about the design of the system, with no results. 
ReactOS Beginnings At the end of 1997, the project had burnt out with nothing to show. Jason Filby became project coordinator and called on everyone still subscribed to the list to revive the project. It was decided that the target should be Windows NT and that there would be an emphasis on results -- on written code rather than endless talk. The project was renamed ReactOS, since the operating system's roots grew out of a dissatisfaction with Microsoft's monopoly over the operating system market. In February 1998, ReactOS began. 
Steep Climbing The first few years of ReactOS were painfully slow, despite the large amounts of code that was being written. Only a few of the developers knew how to write kernel code. It was a time of only a few people writing the difficult kernel beginnings. Later, as the kernel became more complete and stable, as basic drivers such as the IDE and keyboard drivers were written, more people were able to get involved in development. 
Today The kernel has come a long way and is quite stable and many APIs are complete enough for higher level work to be done. Substantial work has been done on many libraries. Networking code is getting close to being usable. A basic implementation of the Graphics Device Interface (GDI) and windowing code is in place. The amount of developers are steadly increasing. The first applications are working, including some relatively complex ones like AbiWord.
Relationship with the WINE project ReactOS has been working with the WINE project to share as much programming effort as possible. This mainly concerns User Mode DLLs. Other areas of cooperation lie in applications and testing suites.
Website You can find more information (including how to get involved and how to obtain the software) on our website, http://www.reactos.com

LiveCD A LiveCD, allowing you to run ReactOS without having to install it on your computer, is available.