A normal web page would probably have a link to the license information, but since you can't put links in CSS pages the author just had to make it open source.
I know it has nothing to do with CSS, and it is technically possible to have a link to something useful when using a pretty design, but I have yet to see an example. Judging by the 25 (now 26) karma I lost I think a lot of people here really like good looking pages with no links or information.
Please don't address other users aggressively on Hacker News.
Consider how much better this comment reads if one deletes the first sentence. It goes from being a bad HN comment to a good one immediately.