And that's where the information stops. As I recall, the IAC is actually incorporated as, or is the successor to, a daycare center.
Some FReeper did some snooping around regarding contributions to the WWP -- which, being a political party -- requires some level of transparency. They came up with one contribution of sufficient size to warrant reporting. As I recall, some foundation of uncertain heritage gave $56,000.
Where the rest of the money comes from, though, is an unanswered question. It's worth noting, however, that Iraq's Ambassador to the UN has been a featured participant in many of the IAC's seminars.