This is not a theft. You used the plugin from the github, didn’t even bother to check the license, used someone elses work with small fee. Guy even returned you

This is not a theft. You used the plugin from the github, didn’t even bother to check the license, used someone elses work with small fee. Guy even returned you the money. It’s probably some kind of dark pattern, but certainly not a theft. Pay the plugin and you’ll not have to pay the fee.