Chorus from Chorus Systems, Inc.

http://www.comp.lancs.ac.uk/computing/users/pr/www/chorus/faq.html

CRTX from StarCom

http://www.n2.net/starcom/

FX-16 Intec Inoventures

http://www.islandnet.com/~iii/iiisoft.html#fx16

iRMX from Intel

http://www.intel.com/design/irmx_os/

LynxOS from Lynx Real-Time Systems

http://www.lynx.com

Mach from Carnegie Mellon University

http://mmmc.jaist.ac.jp:8000/projects/rtmach.html

http://www.cs.cmu.edu/afs/cs.cmu.edu/project/art-6/www/rtmach.html

Nucleus from Accelerated Technology

http://www.atinucleus.com/

OS-9/OS-9000 from Microware Systems Corporation

http://www.microware.com

http://os9archive.rtsi.com/os9faq.html

OSE from Enea Data

http://www.enea.se/ose

Precise/MQX from Intermetrics

http://www.inmet.com/MSD/kernels.htm

PSOS from Integrated Systems

http://www.isi.com

QNX from QNX Software Systems, Ltd.

http://www.vir.com/vir/QNX-info1.html
http://www.qnx.com

RealIX from Modcomp

http://www.modcomp.com/hotproducts/pcrealix.html

Real-Time UNIX for the Power Hawk and Night Hawk Systems from Harris Computer Systems Corp.

http://www.hcsc.com/real_time

smx from Micro Digital, Inc.

http://www.earthlink.net/~mdi/product.htm
http://www.earthlink.net/~mdi

VRTX from Microtec Research

http://www.mri.com/vrtx.html
http://www.mri.com

VxWorks from Wind River Systems

http://www.wrs.com