RTAI home page: https://www.rtai.org/index.html
NMT's RTLinux home page: https://www.rtlinux.org/
KURT home page: https://hegel.ittc.ukans.edu/projects/kurt/
Information on all variants of real-time Linux: https://www.realtimelinux.org/
GPL development tools, commercial support and a validated RealTime Linux installation CD: https://www.zentropix.com/