Hi Sylvia,
Not sure if you saw Stewart Mader's presentation at the conference, his wiki in education book authors retain their own licenses for their chapters and the book itself has its overall license.
http://www.wikiineducation.com/display/ikiw/Home <-- link to the copyright
In fact, the way this book is structured is a good example for us too. Maybe we can look into our book being complimentary to Mader's. Just a thought.
Hope that helps
Robin