You can't copyright an artistic idea. Hence, floating mountains can't be copyrighted. Next...
Why not try reading the document first? Parts 49 and 50 are particularly interesting. Apparently people in the production had stated that they were given Dean's work to base Avatar items and markings on.
Entertainment Weekly reports that Cameron was asked in 2010 if he got the idea for floating mountains from a Yes album cover, and answered: “It might have been, back in my pot-smoking days.”
One would have thought that Cameron would have learned his lesson by now.