Yes, because there is a basic assumption. Those projects aren't consumer-facing games. Those are hobbies. You know it and you are simply arguing in bad faith. I know actual game developers who released their games for free or under a pay-what-you-want model. They refuse to do so again because they can't support themselves by doing it. I am a game developer and I won't release my games for free because I need to support myself. There is all the data you need. Find me other data saying otherwise.

It depends on the system. In taxes, yes. Use isn't tied to paying. In consumer goods and services, they are not paid by taxes. So they do have a direct use/buy causation.

Yes, of course. They created the design, it cost them time and money, you want to use it, so you should pay part of those costs. Or to put it differently: You both use the design, why should they be the ones to pay for its creation, and not you?