Hi,
I came across this post from the CC News feed that Cookbookers might be interested to read: http://thefoodgeek.com/miscellaneous/who-owns-that-recipe
Thefoodgeek.com is licensed CC-BY so I think their material could be repurposed in the Cookbook if desired.
Incidentally it might be useful if the Cookbook had a page listing other freely licensed recipe/cooking resources.
cheers Brianna