Eric, the author, says he won't accept any puzzle submissions because of attribution and legal issues. This seems like the wrong outcome for people who want to make the site better but don't want credit, compensation, or attribution.

Has anyone seen a site using an IP assignment agreement which is the equivalent of "take my work, I don't want credit, and it's just for your site"?

The Creative Commons CC0 license comes closest, but one could scrape those puzzles and create a competing site, which I'd guess Eric wants to avoid.