That link is the official story I am aware of, where can I read about that one?

I have a paper copy of a paper (in French) about SOS Interface. Had scans of this at one point.

There is a bit more of a timeline in a talk [1] he gave at INRIA a couple of years before he died.

[1] https://www.inria.fr/en/jean-marie-hullot-perforated-cards-i...