For referencing Project Gutenberg better read about that on http://www.gutenberg.org
It is either the complete legalese from PG or no reference at all.
Then I would include it all. Indeed, my initial impression was that all the PG legalese should be retained, on separate pages. They did a ton of work on those etext and really should be credited for it in any works derived from it, even if they do not demand such credit.