After taking a quick look at the surface, Edgar Mitchell appears to be a credible guy, but I could be wrong. Over at his official website, his articles and essays are available for viewing. I haven’t had the time to view all the papers, but I think they would give some insight into any alternative motives for his recent release of UFO/Alien news.
Also, I found this video over at the official Edgar Mitchell message board.
I’ll get back once I’ve had time to view his papers with a more detailed eye.