Why? Are people with deep technical knowledge, both soft and hard, not allowed to profit from that knowledge? Can you point to some conflict of interest in writing a book, speaking, and being a professor while a private citizen? Are you just against capitalism?
The man spent his entire adult life in service to this country and never profited from it while in the act of that service, which you can't say for many of his colleagues.
that right there is unacceptable to me.