Go ahead and prove that.
I would say he is right. Most big open source projects have some company behind them.
WebKit, Flutter, Qt, VSCode, Tensorflow, React, WebKit, LLVM, Rust, Go, Kotlin.
Counterexamples: Blender (though initially it was commercial), VLC, Godot.
> Webkit
Yes, commercial open source projects exist.
Parent and you say 'most'. Github says it has 200M projects on it, do you really think >100M of those are commercially funded? I don't think it is possible.
Its amazing how much easier its gotten to make a living working _with_ open source code over the years, while it's still often hard for the actual developers/maintainers to get any funding (e.g. ssl, ntpd, etc.)
It also seems that companies don't get generally get involved until some 'critical mass' is hit, leaving volunteers, uni's, and foundations doing the initial work (eg linux, apache, NSCA Mosaic, ssh, gcc, glibc/dietlibc/etc, php, perl, vim, nim, ruby, etc.)
Even taking from your examples - LLVM started as a uni. project, Webkit was forked from KDE's KHTML, and Rust was a personnel project for years before Mozilla got involved..
edit: god I need coffee. fix poor sentances.