Thanks for the hint. vocho/openqnx has about 200 forks, and many seem to have been maintained. The original vocho/openqnx repository is the result of the MONARTIS (MONitoring Application for Real-Time Industrial Systems) project conducted in 2009 at HEIG-VD (https://heig-vd.ch/), Switzerland. The _NTO_VERSION define in <sys/neutrino.h> indicates that it was based on QNX version 6.4.1. I've created my own fork and am currently studying and minimizing it.