Question

A stand-up comedian performs paid shows. During any given period he has one prepared act that he simply takes around to different venues with small changes. Someone who attended the show remembers the jokes and tells them to his friends. He doesn’t write them down or publish them. It is known, at least from what people have been saying, that there were some who decided the jokes were great, but there was no longer any point in going to the show because most of it would already be familiar. I asked a lawyer friend, and he said that as far as the law goes he is not aware of any prohibition like this. What about Jewish law?
The same applies to someone who heard a lecture. Say Amit Segal has a different lecture each period that he gives for pay in all kinds of places, and once someone recorded it and uploaded it and there was a big fight about it. So if I remember all the ideas, is it possible that I’m forbidden to tell them verbally to my brother, because then presumably he won’t go? Even if without that he would have gone?