Once again the SDMB comes through!
Thanks a lot everyone! I think we have a final correct answer, John Charles Farrow, as discovered by Ellis Aponte Jr.
Many thanks to all who participated in the thread, but especially postcards, Ms Boods, Gary T, K364 and Ellis Aponte Jr.
A synopsis of the thread:
Photo 1: airbrushed photo from Donovan CD
B&W Photo (photo 1) from Donovan CD picture book is shown here. Photo has someone airbrushed out.
http://nouilles.info/sdmb_questions.html
Photo 1 shows (left to right) Donovan, Mia Farrow, George Harrison, Maharishi Mahesh Yogi, Paul McCartney, John Lennon.
Someone standing in the back between Donovan and Mia Farrow has been airbrushed out (and also, if you look closely, someone standing to the right of John Lennon from the viewer’s perspective.)
Photo 2: similar group photo in colour
Lute Skywatcher in post 4 shows a colour photo (photo 2) that clearly comes from the same photo session (note clothing and accessories)
http://www.flickr.com/photos/35935603@N03/4402347874/
Photo 2 shows, from left to right:
Cynthia Lennon, John Lennon, Mike Love, Maharishi Mahesh Yogi, George Harrison, Mia Farrow, Donovan, Paul McCartney, Jane Asher, Patty Boyd.
Exapno Mapcase in post 8 shows us some photos of Donovan’s friend Gyp aka Gypsy Dave. (Which, as we will find out, is not the missing person.) P.S. Exapno, I didn’t think he would have been the one airbrushed out because in my CD booklet, Gypsy Dave is mentioned and there is a photo of him. Why show him in one photo and airbrush him out of another photo?
Photo 3: Bungalow Bill
Harvy the Heavy (post 9) says “maybe it was Bungalow Bill” which at first I thought was a joke, until I learned that “Bungalow Bill” (the song) was inspired by a young American who was at Rishikesh in 1968. The young American was named Richard Cooke and K364 (post 13) links to a photo of Richard Cooke here:
http://www.thealohabear.com/bungalow-bill-the-real-story/
Breakthrough
Photo 4: unairbrushed photo
postcards in post 11 finds the photo unretouched (in the Phillip Norman book SHOUT The Beatles in Their Generation), showing the missing person! Thank you postcards, I owe you one.
You can see the photo (photo 4) here:
Photo shows (from left to right)
Donovan, Mystery person 1 (the question in the OP), Mia Farrow, George Harrison, Maharishi Mahesh Yogi, Paul McCartney, John Lennon, Mystery person 2.
Photo 5 (a and b): Derek Taylor
Gary T in post 15 thinks it might be Derek Taylor. Links to several photos, thinks these are the closest to the Mystery person:
http://www.jfkmontreal.com/john_lennon/graphics/derek_taylor.jpg
Photo 6: similar group photo in colour, same as Photo 2
Ms Boods in post 17 finds a full-colour photo which happens to be a mirror image of Photo 2. She says you can find this colour photo in Roy Carr’s The Beatles: An Illustrated Record (2nd edition, pg 72).
Her suggesion: check the book The Beatles in Rishikesh by Paul Salztman.
Photo 7 (a and b): similar group photo, in colour, showing our Mystery Person
Linked to by Ms Boods in post 18
from left to right:
John Lennon, Mike Love, Maharishi Mahesh Yogi, George Harrison, Mia Farrow, Mystery Person 1, Donovan, Paul McCartney, Jane Asher, Patty Boyd
postcards (post 21) comes through again with a better scan of photo 7 a. He finds it in The Beatles Anthology (p. 286) as mentioned by Gary T in post 15.
from left to right:
George Harrison, Mia Farrow, Mystery Person 1, Donovan, Paul McCartney, Jane Asher, Patty Boyd
Photo 8 (a, b): Magic Alex
Ms Boods (in post 17) guesses it may be Magic Alex.
Lute Skywatcher (post 25) shows another photo of Magic Alex and Ms Boods retracts her guess.
The winner (or at least so I think)
Video: John Charles Farrow
Ellis Aponte Jr. in post 31 links to a youtube video showing Mia Farrow’s brother, John Charles Farrow, who according to Ellis was 21 years old in 1968 and was present in Rishikesh when the Beatles visited.
John Charles Farrow is the contestant on the left, 10 seconds into the clip
needscoffee (post 33) adds:
If you pause it right as he smiles at around 6:52, it sure does look like the guy. And around 7:20.
K364 (post 35) confirms that Mystery Person 1 is John Charles Farrow, according to “someone who was there”. K364 also says that Mystery Person 2 (see Photo 4) is Nancy Cooke de Herrera, mother of Richard Cooke aka Bungalow Bill.
My conclusion: I am convinced that Mystery Person 1 is John Charles Farrow, from seeing him in the youtube video. It also would seem logical since the mystery person is standing right next to Mia Farrow.
Question: why was he airbrushed out? My first thought was, this is someone Donovan doesn’t like, but now I think, as suggested by Exapno Mapcase (post 8) that he was airbrushed out because it increases the sheer awesomeness of the photo if only major celebrities are show. GuanoLad (post 30) says “maybe he was airbrushed out because no one could remember who he was” but I doubt that if he was the brother of Mia Farrow.