I think there are a lot of high profile opensource projects which are either run by corpos (like React) or have a lot of full time employees submitting code (Linux). But there’s an insanely long tail of opensource projects on npm, cargo, homebrew etc which are created by volunteers. Or by people scraping by on the occasional donation.
"unpaid volunteer working full time" also doesn't sound like something that someone would believe. Full time and unpaid rarely go together.
Most of the Linux foundation projects, which includes Node are volunteers. Most of the Apache foundation software is from volunteers. Most NPM packages are from volunteers. OpenSSL is volunteers.
There is also a big difference between the developers who are employees on salary versus those that receive enough donations to work in open source full time.
The survey found that specifically linux code is dominated by people who are paid for it.
> Most of the Apache foundation software is from volunteers.
Large Apache project specifically are backed by companies per Apache rules. Each project must have at least three active backing companies. They contribute the most of the code.
Yes the kernel code, but the Linux Foundation projects (mentioned in the comment you quote) are MUCH more than the kernel.
See the list on https://www.linuxfoundation.org/projects
Not a lot of applications being maintained by altruists, but look under the hood in Linux/GNU/BSD and you fill find a lot of volunteers motivated by something other than money.
I think there are very few projects that do not accept support in any form.
For a lot of single developers that's not a thing they're ready or able to do. Those that can, usually have companies established as a revenue source for their OSS project.
The need for this invoice is because companies cannot justify irrational spending. The have no process for gift-giving. There is almost nothing that will make spending on OSS not irrational, unless you're paying for specific bugfixes or customization work. You can't issue an invoice for nothing. How much would the invoice be for?
edit: that being said, please continue to make up any pretense to get OSS contributors paid if that's working for anyone.