I am curious about why linux would be chosen as the OS instead of something a bit more battle-tested like QNX? (with the upside of the ability to go hard real-t

I am curious about why linux would be chosen as the OS instead of something a bit more battle-tested like QNX? (with the upside of the ability to go hard real-time if necessary...) I love Linux, but the thought of trusting my life to it gives me the willies?