Well, for anyone intrested in hosting a tournament, for oa or anything else really; here is a tournament organizer, supporting brackets for single elimination, double elimination, and round robins.
http://www.nealpro.com/And yes, it was originally designed to host gaming tounraments(specifically super smash brothers melee). For the elimination brackets, you can randomly seed people based on location and/or skill level, making sure good people dont face good people, and that people who live in the same area wont knock each other out(basically so that your older brother doesnt knock you out first round
). So basically, it just gives people options when considering competitive and organized gaming.
or you could use the openarena league tournament, I am not sure what they are using, but it seems to work just fine