Wow! What an achievement for those devs.

https://www.rtems.org/applications/

It’s a missile OS so this isn’t particularly surprising.

Amazingly enough, things can be surprising when you don't know anything about them, regardless of their intended purpose.

But I suppose forums/Internet can be grumpy about other's amazement.

"Wow, this RTOS runs on RTOS platforms!" is an apple that loses it's shine after ~2 or 3 days in the robotics profession.