Yes, I've heard many authors saying that they're unhappy with the emergency library in particular because they are concerned they won't be able to get paid to write books if this happens. And, based on my training and experience, if someone isn't paid to do their job anymore, they'll look for another job.
I'm aware of GitHub. I've published things to GitHub myself. Many of them I was paid to publish. There's a lot more I would publish to GitHub if I weren't writing proprietary code all day. You can go see all the pull requests I haven't responded to. I think it's absolutely true that if you gave people a way to put a roof over their heads and food on the table, they'd do work they love anyway, and I myself point to GitHub as an example of that. I think it's also true that if you don't give people a way to put a roof over their heads and food on the table, they'll find something else to do with their life that does.
I've also visited Wikipedia. Here's a quote from the first person to make one million edits: "Being suddenly and involuntarily unemployed will do that to you." I think that demonstrates that if he could do something else and get paid for it, he would have.
I gave an example in the context of encyclopedias where vastly more articles of at least equal quality ended up being written.
I'm asking for any citation you can give of trends that go in the opposite direction of encyclopedias, music recordings, blogs, citizen journalism, propaganda, to name a few. It's my observation that when the cost to publish and read hits essentially zero the amount of content goes up, not down.
https://www.fossjobs.net/ https://github.com/fossjobs/fossjobs/wiki/resources
And yes, some FOSS is subsidized by companies who pay their engineers to contribute, but there are also people who contribute on their own time.
It's certainly possible to argue that copyright is so bad that we should have way fewer authors and musicians in this world, such that only those who are truly passionate about writing and making music (and/or independently wealthy) will do it, but it doesn't seem to me that that's what people are arguing.
Isn't it already very well established that FOSS is currently largely being built by people employed by corporations? They are most definitely not unpaid.
Have you done or read research to suggest this is something to worry about?
There are other concerns certainly. But I have trouble understanding how someone who has ever visited Wikipedia or visited github could even ask this question. It sure sounds like a conceptual anachronism to me. (Though not nearly as bad as the person who wanted to shift from discussing copying data to holding up a bank the last time this topic came up.)