I followed the same chain of logic as you; certainly looks like gmpg.org has been compromised. The entire root domain that the cert is signed for (fotomateo.com

I followed the same chain of logic as you; certainly looks like gmpg.org has been compromised. The entire root domain that the cert is signed for (fotomateo.com) is on Chrome's phishing block list too. Odds are that gmpg.org never set up https for themselves. Someone hacked their web server and installed a new Apache instance or VirtualHost config for port 443 without them having noticed. In any case, no danger in loading the OP's article.