Extremely fair point. I didn't read the original post carefully enough to realize that the libre-distributable part was an important quality for the list.
The conditions on pianobook about redistribution are part of a general pattern of sort-of-friendly-towards-FLOSS seen in many of the things that Chris Henson touches. He's a fan of people getting together to do things as a community and making the results available at no charge, but push that just a little further than he wants to go by himself, and you see the limits.