I reached out to the tournament director today and asked your questions as well. It sounds like the scotch doubles is an auxiliary mini-event and at this time, here's the information that is available: open event, sign ups on site, starting at noon CST on friday, single elimination, race to be determined based upon number of entries, $30 per team.
As for the 8 ball and 9 ball singles, they are open to any amateur player, no league sanctioning required. Members of a team for the team event can be sanctioned by any of several different league systems, the most common ones being BCA, ACS, VNEA or GMPA. Contact information is on the flyer for any further questions on that topic.
Hopefully this helps you out and good luck.