Andrea asked a question on launchpad about problems compiling Mosquitto on QNX. I've now managed to get an evaluation version of QNX and fix the compilation problems. These fixes will be in 0.12, but you can get them in the current snapshot if it's urgent. I've also put compiled binaries in the downloads directory but they are completely untested, so use at your own risk.
Although I've provided these binaries I don't intend to keep doing so for each version of Mosquitto. I will endeavour to fix any other problems that arise in the future though.