Issues with the link aside, there's an interesting comment entitled
"MySQL has the better license", which reads:
Someday PostgreSQL might be "embraced and extended" by a predatory
company that will turn it into a closed product, because it uses the
(defective IMHO) BSD license. That can't happen with MySQL, which is
GPL.
Two comments, First, I'm not an expert on licenses so I can't vouch
on its validity with regard to the BSD license. Second, I get the
impression that MySQL itself is more on the way to being closed
source, beinbg as it is owned my MySQL AB who charge for it.