You'll find the exact licensing terms in the IPTC comments in each individual photo. I've left them as I first released them, rather than trying to bring them all to the same terms.
This page was first prepared in celebration of the first International Pixel-Stained Technopeasant Day, which was in turn spawned by this:
I'm also opposed to the increasing presence in our organization of webscabs, who post their creations on the net for free. A scab is someone who works for less than union wages or on non-union terms; more broadly, a scab is someone who feathers his own nest and advances his own career by undercutting the efforts of his fellow workers to gain better pay and working conditions for all. Webscabs claim they're just posting their books for free in an attempt to market and publicize them, but to my mind they're undercutting those of us who aren't giving it away for free and are trying to get publishers to pay a better wage for our hard work.(from this amazingly ignorant post).