Is it permissible for a female medical student to listen to recorded lectures by a doctor who does not approve of anyone other than his own students listening to them, knowing that these lectures are sold?

If the discs are owned by the doctor and he forbids listening to them, then no one is permitted to listen to them without his permission, based on the Prophet's (peace be upon him) saying: "The wealth of a Muslim person is not lawful [to take] except with his willing consent," and "Whoever precedes [others] to something permissible, it belongs to him." However, if he sells them and stipulates that the buyer must not let others listen to them, this is not valid because it falls under conditional sales which are prohibited. It is well-known that such a sale is annulled as long as the seller insists on the condition, but it becomes valid if he waives the condition.