In many countries even donations will still have contractual obligations.
May not be an issue for the dev depending on there country, but patrion is US based.
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Yes, you can go to jail for online scams. The federal government takes online fraud very seriously, and it has a number of laws that make online scamming punishable by jail time.
The maximum sentence for wire fraud is 20 years in prison. However, the actual sentence a person can receive if convicted would depend on a number of factors, such as the amount of money defrauded and the defendant’s prior criminal history.
In some cases, online scammers have been sentenced to much longer than 20 years in prison. In 2019, a man was sentenced to 30 years in prison for his role in an online romance scam that defrauded women out of more than $1 million.
While it’s certainly possible to go to jail for online scams, it’s important to remember that every case is different. The sentence you would receive if convicted would depend on the specific facts of your case.
Also A paywall is counterintuitive to donations, or "a tip jar" as you say. Once you offer anything as a benefit the dynamics change.
Is this worth us debating and beating each other upside the head verbally over, no. Is it he at fault for his actions legally, Maybe, maybe not. I don't know his countries laws, and I am not a lawyer. I also will not dig into international laws.
TLDR
There very well may be an issue but this is not the place to deal with it, but to blindly say everything is kosher is also flawed.