Is there anything halachicly wrong with reselling (on eBay or wherever) something that someone advertised as a free (ltoeles rabim) giveaway, that you responded to and took?
I don’t really know, but look at it this way: If someone gives you a present, can you sell it? Sure you can. It might, however be different in this specific type of situation because the free item was meant to be given freely to ALL. The inention of the giver might make a difference. I don’t really know. Good ethical question.
Why is this issue worth discussing? How much free stuff is out there to be gotten? I think most participants in this discussion are under the mistaken notion that there are large amounts of “free” stuff that is regularly given away.