No affiliation, I just use it for work:
I've used it for school projects and work before, and was amazed by the documentation and API capabilities. Everything is configurable and easy to figure out.
Edit: it's Creative Commons Attribution-NonCommercial 3.0. I wonder if that stops me running ads on a site that uses it.
"The empirical findings suggest that creators and users approach the question of noncommercial use similarly and that overall, online U.S. creators and users are more alike than different in their understanding of noncommercial use. Both creators and users generally consider uses that earn users money or involve online advertising to be commercial"