It is pretty standard, but the narrative is wrong. In reality it's more like this:
Build a little tool for yourself. It's small, it's simple. Someone else sees it and likes it, so you open-source it. People start using it, and it feels good. The hobby project starts consuming more and more time.
Companies start using it. Bug reports and feature requests pile up. Users who see themselves as customers without ever having paid a cent for it start to demand bugfixes and features. Toxic, entitled people kill the mood and the hobby project seriously isn't fun anymore.
Nobody contributes or donates, they just demand.
So now you got a choice: drop your hobby project or go professional.
What you are seeing in the OP or with Thunder REST is the second option: People going professional. Cause that means money is coming in, the main dev can quit their day job and maybe even hire some extra staff to deal with the workload and with pesky entitled users.
So to you now, breadsmasher: You seem to think that you are entitled to free updates for Thundar REST. I guess you contributed significant amounts of code to it or donated significant amounts of money to it?
You did do that, right?
You aren't just demanding other people to work for free for you, right?
Because if you did that, that would be seriously shitty of you. But I'm sure you aren't that kind of person, are you?