ReactOS is a computer operating system intended to be binary-compatible with application software and device drivers made for Microsoft Windows NT versions 5.x and up (Windows 2000 and its successors). It is composed entirely of free software, by means of a complete clean room reverse engineering process.
Although the project is in the alpha development stage as of 2008, many Windows programs already work well. While the ReactOS kernel has been written from scratch, the userland is mostly based on the Wine compatibility layer for Unix-like operating systems.
ReactOS is primarily written …

QNX (pronounced either Q-N-X or Q-nix) is a commercial POSIX-compliant Unix-like real-time operating system, aimed primarily at the embedded systems market. As of September 12 2007, the source of the QNX kernel has been released for non-commercial use.

Description
As a microkernel-based OS, QNX is based on the idea of running most of the OS in the form of a number of small tasks, known as servers. This differs from the more traditional monolithic kernel, in which the operating system is a single very large program composed of a huge number of …