I wonder if he has a book deal coming out?
There have been rumors for a long time about US military operations in space that went well beyond what NASA officially acknowledges. Not aliens, but things beyond the space shuttle
Here are a couple known projects that never made it to fruition:
The Air Force toyed with a project for awhile in the early 60’s called Blue Gemini which was aimed at ultimately putting Air Force astronauts aboard a Manned Orbital Development System. That idea was abandoned to pursue one of a Manned Orbital Laboratory—also abandoned. Everything about the Blue Gemini project was meant to be internal within the Air Force, so the possibility was there for unannounced launches and missions. All that was scrapped by 1969. SkyLab was the civilian implementation of the general ideas.
http://history.nasa.gov/SP-4203/ch6-2.htm
A shuttle-like vehicle, the Boeing X-20-Dyna Soar was another Air Force program aimed at getting Air Force astronauts into space. A mock-up was built but that project was also canned just construction on real hardware began.
https://en.wikipedia.org/wiki/Boeing_X-20_Dyna-Soar
It's a very good market niche for at least one moon-walking astronaut to exploit. Without commenting on the ethics of it, it certainly seems like a good marketing decision on his part.
He and his beliefs are featured in a book about the conjurer with “supernatural powers,” Uri Geller. Mitchell was one of his acolytes, apparently.