If the license distribution on Picasa is similar to
http://www.flickr.com/creativecommons (and it seems to be based on a
small number of trial queries), you'd weed out 2x as much nonfree
stuff by excluding NC than by excluding ND.
Of course they ought to allow both filters to operate on a single query...
p.s. FIST Is a Superneat Tool! I was going to say nice, but couldn't
resist the recursive acronym. FWIW http://www.23hq.com/23/search/ also
allows filtering by license though I don't know how amenable to
integration it is -- search seems to use AJAX.