Integrity
   Secure, no royalty, for high reliability embedded systems; hardware memory protection to isolate and protect it and user tasks from incorrect operation by errors or tampering; object-oriented design allows verifying data security/integrity, communications
   http://www.ghs.com/products/rtos/integrity.html

Integrity (Operating System)
   Growing article, with links to many related topics. Wikipedia.
   http://en.wikipedia.org/wiki/Integrity_(operating_system)

KROS
   Small (12-64k), standards-based, low cost, no royalty, realtime OS; POSIX, ITRON/uITRON programming interfaces, GNU compiler support, source code provided; supports CPUs: Altera Nios, ARM, Hitachi SuperH. Free downloads: demos, documentation, updates. KRO
   http://www.shugyodesign.com/

MaRTE OS
   Realtime kernel for embedded uses, follows Minimal Real-Time POSIX.13 subset. Most code is Ada, but some C, assembly. Hardware access via Abstract Hardware Interface (HAL). Runs in cross development environment: PC Linux Host, bare 386 PC Target, Ethernet
   http://marte.unican.es/

REAL/IX PX
   A POSIX real-time operating system for x86/Pentium based systems. By Modcomp, Inc.
   http://www.modcomp.com/realtime/products/descriptions/8272.html

Roadrunner
   One-user, general purpose OS built on a protected memory, POSIX threads RT kernel; full kernel, device drivers, file systems, and network protocols runs in about 200 K RAM; now runs on x86 CPUs but designed for easy portability. [Open source, GPL]
   http://www.cornfed.com/

S.Ha.R.K.
   Dynamic configurable kernel architecture to support hard/soft/non realtime use with interchangeable scheduling algorithms: fully modular in scheduling policies, aperiodic servers, concurrency control protocols; all not modular in most traditional OSs. Der
   http://shark.sssup.it/