> but there'd probably be a couple weeks of chaos. Does Linus bear zero responsibility because he's a volunteer

Linux Foundation would appoint somebody else on his place and have him sign similar contract. It would be likely a person that is already employed in similar capacity - one of current paid maintainers. No fork would be needed. Linus Torwalds is not a volunteer at this point.

Linus Torwalds will leave linux one day. He wont stay there forever - most likely to retire, but possibly to do something else.

Also, Linux is particularly bad example, because most contributors are paid for their effort by someone.

It is a bad example but most major open source projects are in that regard. However, the community driven ecosystems (Rust, Go, JavaScript ..) have significant components in that particular unpaid maintainer situation. And that is a problem.

Go is done and maintained by google employees. JavaScript specification has syndicate behind it. Rust has clear governance, through I cant find who pays for it all.

Any big enough project will formalize relationships at one point or another - latest when they need to raise money or organize conference. These projects are too big to be run over the weekend, they do have to pay regular staff.