Your son is in breach of the intellectual property rights of the author of the play. What your son has been told is correct.
The amount of compensation that he would be liable for would be the cost that the author would normally charge for a production.
The compensation is the amount of loss which the author suffers as a result of this or the amount of money which he could reasonably have been expected to receive for allowing one production to be licensed.
If he is not famous or has not had any other works ever published, it is not likely to be very much. Low hundreds of pounds at the most. However if your son doesn’t pay up, the author would be faced with taking him to court and it would be up to the court to decide how much is reasonable.
It doesn’t matter that he didn’t make a profit from it or take money.
If this doesn’t end up in court, he has the potential defendants if he can argue successfully that this was not public performance but for a limited number of personal friends. It depends how he knew these people. If this was done, for example, in a Private members club, for the purposes of the law, that is a public performance.
Can I clarify anything else for you?
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