Most of those links are for buying prints of the art, not the digital copy.
The artwork links from Joymonkey (the first set of links) are the digital copies and the $10 donation for unlimited access is just to cover the investment Joymonkey needed to to help pay back purchase of the entire library he made and to cover the cost of hosting the artwork. If not for him hosting the art, much of it wouldn't be available to us at all.