Once upon a time (2007!), QNX made their source code available under a read-only type license. When Blackberry bought them (2010), source code access was shut off.

That was 16 years ago so maybe their opinion on the matter has changed. But they make money (or at least try to) selling a commercial license for QNX so an unrestricted free/open license seems unlikely.

if you're interested in extending, sure

otoh, i'm not - everything has to die sometime

that doesn't mean you have to feel the same - so go for it