I think the person who originally designed the page was proud that he was using FreeBSD and he decided that he wanted to share this information with the world. Doing so would make him happy; perhaps he imagined that a FreeBSD user would one day see the logo and enjoy his life a little bit more because he connected, although indirectly, with another in his tribe.
Little decisions like this are what make you human. Don't let your fears and inhibitions turn you into a robot because some interview with Steve Jobs said not to put "powered by..." logos on stuff. Do what feels right in your heart. Enjoy life first and figure out how to make money without compromising your humanity.
Steve Jobs had a separate set of rules that applied to Steve Jobs. Like free-for-all parking at work, everyone's equal... unless you're Steve Jobs, then you get a reserved spot.
It's on a login page, presumably operated by the ISP if they're the ones responsible for the logo content. Under that condition, why should they be prevented from advertising what technology they use? Should they also be forbidden from using their own name?
Removing the "Powered By" makes the world a worse place?
I am inclined to agree with one of the later emails in the thread; "Powered By <blank>" doesn't really belong on end-user pages in the first place.