At a summary level, Aruba Instant supports URL filtering against OpenDNS. All DNS requests are redirected to OpenDNS. If permitted, OpenDNS will send back a resolved IP address. If not, the HTTP request will not go further.
There are more advanced options added in 3.0 and those are managed by OpenDNS themselves. Basically, you can add the IAPs into your OpenDNS account and configure advanced features like security, content filtering, blacklist, etc.