For those that care, I have an answer to this one.
I won't use his real name, since it doesn't appear he used it professionally, but as a writer, M.D.R. went by the name "Del Rayburn."
As "Del Rayburn," he co-wrote an episode of
Death Valley Days called
"A Man Called Abraham" that aired on June 21, 1967 (Cushman doesn't make it clear that this script, mentioned in one of Rabyurn's letters to Roddenberry, was actually produced — probably because he didn't bother to check). Somewhat ironically, as "Del Rayburn," he also authored an educational cassette tape titled "How To Write Fiction That Sells" for Gordon McLendon's "Car-Teach," which quickly failed as a business venture (
see page 198 of this book). He also appears to have written several pulp western stories in the mid-1940s (a quick eBay search will pull up a few examples).
None of this, honestly, is particularly relevant to
Star Trek. M.D.R. is far from the only writer who sent an obnoxious letter to Roddenberry (though his may be the longest I've read) during the run of the series. His inclusion in
These Are The Voyages, like many other things found in those books, is pointless filler to justify making the series a three volume set.