This guy worked for free, for that Peyo company! Making a game about stupid smurfs, without charging them any cent, and without getting any cent in other ways, advertising their products in other platforms. I wouldn't pay a cent, no lawyers need to be involved.
They need to complain legally in the country were that guy lives. That costs money. They need to have associates, if not, they have to do it themselves. I think it's a scam, or something to scare the guy. I do understand that companies need to protect themselves, but in this case, no one was making money with their products. In fact they are the only ones that benefict from this.