An alumnus is any male that has matriculated to the school. You do not have to graduate from said school to be an alumnus(a). The term refers to any former student, graduate, drop-out, transfer, whatever. If the student was a female, she would be an alumna, and if it were a group of females only, alumnae (still pronounced like alumni).I don't believe so but I definitely could be wrong. Alum is a term many broadcasters/sportswriters use loosely to describe them as having attended that particular school. People who do so probably aren't actual alums of any school or they would know the difference.
Edit: I should always read the whole damn thread before responding. The problem is I'm too lazy to go back, so, if I don't comment right away, I'll never comment. Like I said, I should probably read the whold damn thread first.