Whether or not Sid's interpretation is correct, I don't see any difference between this and quotes from copyrighted written material which often appear. eg Quotes from manuals/textbooks posted by contributors in support of their argument in a discussion, news items from newspaper/tv websites (which I frequently post myself.)
If the artist complains, I'll remove the thread from Rotorheads - but I'd also ensure neither he nor his work are ever given any publicity in any Pprune forum under any circumstances.
Heliport