After a quick read - looks like they have a DNS server that points the supported sites (VPN should work for any site) to their own machines.

So you change what DNS server your systems use to theirs. When you ask for the IP address of say hulu.com you don't get the IP number of the real hulu.com, but their machine that will relay traffic to/from hulu on your behalf...

Less resource hungry as there is no encryption of the traffic between you and them as there would be in a VPN. But if hulu changes things around, things might not work until strongDNS updates their records to the new reality.