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Not quite. He needs _paying_ users. Those don't necessarily grow in the same fashion and under the same circumstances as non-paying users.

That’s true, but maybe there is a probability you can multiply to get the revenue? Just like freemium users

I think it means whatever you want. I read it as if you are able to make money using Caddy wouldn't it be fair to share it with the developer. I think there is a sub-text that implies if you sponsored Caddy and needed some extension or support that is available also. Before Open Source was codified the was an attitude where the software is free but the documentation costs money.

It sounds like you think there's some conflict there, but I don't think they're making any claim that developers don't need income/support/food (they pretty much state the opposite) or that open source projects don't need developers to (continue to ) be developed. The project isn't the developer, the users aren't the donations.