Is there anything in his communication to you that suggest he intends to resell it to their client and profit himself? Because if there isn't, I suspect this is

Is there anything in his communication to you that suggest he intends to resell it to their client and profit himself? Because if there isn't, I suspect this isn't something to worry about even if he legally can. He probably doesn't even realize he legally can unless you tip him off to it. He may just be trying to match-make you two. In which case, drop your original client out of the communication loop as soon as possible, and deal directly with the new client as a fresh entity from which you can only gain. You are under no obligation to: give the new client the same terms as the old client, agree to do any work at all for them, etc.