George Lucas likely had no real impact on the final product. He is given (correctly) the "Based on the characters created by...." credit, but the writing credit is solely Arndt, Kasdan, and Abrams. If Lucas had anything to do with the new characters or any story elements, he would have been given a "Story by...." credit.
Contrary to IMDB, which is easily edited by users (like Wikipedia), George Lucas was given no official story credit. Even Lucas admits that Disney threw out his story treatments.
http://www.ew.com/article/2015/11/20/george-lucas-star-wars-force-awakens-breakup
God knows he definitely had nothing to do with the final screenplay. The dialogue is too believable.