I wouldn't say open source code solely trained the models, surely there are CS courses and textbooks, official documentation as well as transcripts of talks and courses all factor in as well.

On another note, regarding AI replacing most open source code. I forget what tool it was, but I had a need for a very niche way of accessing an old Android device it was rooted, but if I used something like Disk Drill it would eventually crap out empty files. So I found a GUI someone made, and started asking Claude to add things I needed for it to a) let me preview directories it was seeing and b) let me sudo up, and let me download with a reasonable delay (1s I think) which basically worked, I never had issues again, it was a little slow to recover old photos, but oh well.

I debated pushing the code changes back into github, it works as expected, but it drifted from the maintainers own goals I'm sure.