I just emailed the author of the article (Seth Stevenson) to see if he would let the mapmaker know about his map being mentioned on Hacker News. Maybe we can get some contact info for those of us interested in purchasing the map. I know I would be interested in one.
I Googled the URL and found a link to https://github.com/patdunlavey/imusgeographics.com
Seems this gave me access to the entire site - from behind the scenes.
If you go up one level you get the rest of Pat DunLaveys sites that he manages.
Appears to be a lack in security and decisions.