I can see the cause for concern, but I'm very comfortable with it for the following reasons, although I'm certainly not an attorney.
1. Everyone is guaranteed to get a card from the set.
2. The value of that card is ascribed by a secondary market.
3. Given 1 and 2, it's not much different than what card companies do when they create a product - some cards are more desirable, and therefore "worth" more on the secondary market. The difference is that I'm not creating the product; I'm outsourcing it from several decades ago.

4. I give away one slot in every break. (P.S. details on this giveaway
here)
Thanks for asking, and as Leon pointed out, I think it has been hashed out in other places as well.
On a separate note, the break is sold out and scheduled to broadcast on Wednesday afternoon at 4:45 PM CST. Link to the
break broadcast page is here.
Thanks again,
Justin (Burl) Burleson