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/

Shugyo Design Technologies, Inc.  
   Makes KROS, small (12-64k), standards-based, low cost, no royalty, commercial realtime OS; POSIX, ITRON/uITRON programming interfaces, GNU compiler support, source code provided; supports CPUs: Altera Nios, ARM, Hitachi SuperH. Free downloads: KROS demos,
   http://kros.shugyodesign.com/

Locamation Industrial Computer Products  
   Makes ARTOS RTOS: mature, 32-bits, POSIX, for Intel and Motorola CPUs, new features added yearly: latest ISDN communication technology, Flash file systems, Java support, OCXen for Visual C++, Delphi and Visual Basic applications, and Internet server facil
   http://www.locamation.com/locam01/05_Real-timeSoftware/artos.htm