Just to clear everything up, he wouldn't have had to download a program but there are some with a big 'hack forum now' button if he so desired.

Here's a tutorial on how you could exploit the old boards using just firefox and notepad
http://milw0rm.com/id.php?id=871. As you can see, he really didn't have to use any skill at all just following that tutorial to the letter would get him full admin. Had he actually been responsible, he could have made a post from an admin account or something like that - but he chose to delete all the posts. What a prick!