Alfonso,
It depends on what "public" means here. If admission is being charged or the meeting is being held in a public place like a shopping mall or public building, that is one thing. If it is a small group of friends meeting at someone's house, that is another.
Just as a person is entitled to play purchased records, CD's and DVD's at parties and private social gatherings, he has the same right to play recorded lectures. On the contrary to Ms. Hsieh's shaky explanation about her intellectual property rights and either-or crap, if she tried to impede Mike for playing her lecture at a private event, she would be guilty of trying to violate HIS property rights, not protect hers. If she complained about it in public and called it a legal infraction, she would even be guilty of libel.
He bought the course and paid his money for it. He fulfilled his part of the contract. She offered it for sale. Nobody forced her. I don't care what her contract is with TAS. Even if their contract expired, TAS still has the right to sell left-over stock unless the contract specifically states that all copies manufactured up to the point of termination of the contract are to be destroyed. AND EVEN THEN, someone who bought a unit has the right to resell it at any time he damn well pleases and the purchaser gets all private performance rights transferred to him when he buys it.
So it is no longer Ms. Hsieh's right to tell Mike with whom or where he may use his property privately.
There is an ugly non-PC name for that. It is called Indian giver. Our laws do not sanction such a policy and neither does Objectivist morality. Ms. Hsieh should be clear on that if she isn't (and it doesn't sound like she is).
Clarity can be found in the nature of the group Mike has set up. If it is at a stage where it can be seen as a private gathering, there is no problem at all with playing the material for the group—not even if he made some publicity (such as making public announcements, like here in the Events forum). No income would be involved, not even indirect income. And the event would not be open to the public, except to the extent a private party could be reasonably understood as open to the public. If it is a public meeting with the characteristics of a public event, especially if it included advertising, like placing ads in newspapers and so forth, and charging admission or limiting entrance by use of tickets, etc., or if the CD were used in a place of public commerce owned or operated by Mike like a restaurant or clothing store, or even broadcast on radio, TV or the Internet, then this goes off into performance rights and Hsieh would have a legitimate grievance. Mike bought the CD for private use, not public use. She did not sell those rights to him.
Now if somebody thought all this was academic because so few people give a damn about an obscure philosophy course hardly anyone wants to listen to by an obscure Internet author, and he just wanted to drive Hsieh nuts and tempt her to embark on a long intense moral condemnation spree, he could produce a video mash-up using parts of her voice from the course as audio under images of wild savages juxtaposed with lavish coronation scenes from silent movies and gags from the Three Stooges and post this on YouTube, or use her voice sampled on a gangsta rap song about wasting all the motherfuckin' pig enemies or something like that. All this falls within fair use and is perfectly legal depending on the size of the excerpt.
Hmmmmmmm...
(pause... thinking... looking off in the distance with a small degree of inner pleasure...)
Nah... I've got too much on my plate right now as it is...
Michael