If you're talking about Dolphin, read the article again. Nobody refused, but a few people couldn't be contacted - unlike Linux, Dolphin has never required real names from contributors, so this mostly consisted of a few people who contributed under an alias a few years ago before utterly vanishing from the Internet.

EDIT: disregard; didn't see the graph, and wasn't previously aware of the one person who refused. See https://news.ycombinator.com/item?id=9600204 for the correct answer.