It was the first of April, and work on QRV — my port of QNX to RISC-V — was in full swing. A couple of weeks earlier I had put up an open petition asking QNX Software Systems and BlackBerry to re-license the historical 2007–2009 QNX Neutrino source under Apache 2.0. Around this time a thought settled in: there's a real chance it gets ignored completely. I needed a plan B. I've kept the L4 microkernel in the back of my mind for a long time. I first read about it in the early 2000s, along with its various implementations — the ones with the nutty names (Hazelnut, Pistachio), and the one with the funny name, Fiasco, from the group in Dresden. I met those people in person about ten years ago. I never really stopped thinking about L4 after that; I knew about L4Linux and the rest. And I got particularly interested when I learned about seL4. What seL4's authors did still strikes me as a genuinely novel approach: a real microkernel with a machine-checked proof of functional corr...

I came across an old post of mine on the comp.os.qnx newsgroup, dated August 7, 2003. The subject line was "A free QNX-like operating system," and under it I announced RadiOS — a hobby effort to build a free, QNX-compatible microkernel OS for x86, with the microkernel and task manager written entirely in NASM assembly. About 70% of the required system calls were in place by then, along with parts of libc, a console resource manager, and an ATA/IDE driver; there was no filesystem manager yet. The post asked whether anyone wanted to help hack on it, and signed off with "73!". The thread is here: https://groups.google.com/g/comp.os.qnx/c/srdvVoik37M The fuller picture survives on the old SourceForge page, still up at radios.sf.net . RadiOS targeted system-call compatibility with QNX Neutrino 6.1; its Task Manager mirrored the QNX process-manager message format, and its libc was derived from QNX 6.1 code. By mid-2004 it ran to roughly 45,000 lines, almost all NASM, w...