is this some kind of hack?

[Schultz]

No there was people that where direct linking to images on our site So i put a method if they don't originate from our domain you get that image.. This constitutes a problem if your browser isn't sending a HTTP Referer in the header then you get that problem.. where this might cause a problem is if you have a firewall program on your computer and it removes all of this.. You need to turn that off.. Anotehr site i run this on and you can read more about posibilitys at
http://vobsub.edensrising.com/leech.html