Found this on Reddit:

Joesph Campbell, noted mythologist and author of "The Hero with a Thousand Faces", expressed his thoughts on "Star Wars" in an interview. Since "Star Wars" was inspired by "Dune", does anyone know what Campbell thought about "Dune"?

UPDATE: After reaching out to the Joseph Campbell Foundation, I received (to my delight) a very nice response, shown below.

"Regarding your question about Joseph Campbell's thoughts on Dune, to the best of our knowledge Campbell never read any of that series. Science fiction was not a genre that he followed. In fact, he only learned that Star Wars existed when George Lucas publicly acknowledged how Campbell's work had influenced the film (Lucas invited him to Skywalker Ranch to view the first three films in the trilogy – Episodes IV, V, and VI).

I know that's not what you were hoping to hear. Thank you though for your question, and your passion for Joseph Campbell's work."