relatively secure forum software
seems like the dominant choice is vBulletin; apparently they did have a recent security issue but likely every significant piece of software's going to have one or two. I'm a little wary of Phorum and PHPbb because they seem to have had a number of recent issues, but maybe everything's all cleaned up.
I'm thinking mostly of something that's PHP and MySQL/Postgres based, but am willing to hear about other things, too - it's not essential that it be free, but that never hurts either.
