It was a look-but-don't-touch license, and source was only available for parts of the system (I don't think you got the microkernel secret sauce). After QNX was bought by Blackberry, all the community features quietly evaporated.
Here is a good example of the new, caring, Blackberry side of QNX:
I was always a bit surprised that I never heard of an effort to create a GPL'd QNX clone. Do you think that L4 has more conceptual purity with performance and stability close enough to QNX?
I've never used L4, sorry. But I do know that the two operating systems are completely unlike each other. L4 is a bare-bones hypervisor task/switcher kernel. QNX is a complete Unix, which is (to me) where all the value lies.
How L4 compares with the QNX kernel, I don't have the knowledge to comment on.
Here is a good example of the new, caring, Blackberry side of QNX:
http://community.qnx.com/sf/wiki/do/viewPage/projects.commun...
Foundry27, their hobbyist community site, is now a desolate wasteland.