I'm curious as well, I know the site has special somethings to keep track of who invited who, but is the $5 reward automated or do you have to contact Tom?

BYOND wrote on http://www.byond.com/members/[usr name]?command=referral:

Earn rewards with the BYOND Referral Program!
The best thing about BYOND's community is the people who make it. You make the games, you play the games, you share the games. BYOND's players and developers keep everything going. BYOND's members keep BYOND going. We'd like more of both, to make our community as great as it can be.
You can help introduce new people to BYOND, and earn some rewards for doing it. When you use one of the buttons below to link to BYOND, people who visit through your link may decide to stay. You can even invite people to visit your favorite games directly, so if they like the look of a game's banner or icon, they can follow it to see what that game and BYOND are all about. And if they become BYOND members, you'll get a thanks from us for making our gaming family a little bit bigger. For every visitor you refer who becomes a member, you'll get a bonus of $5 in your BYOND Wallet.*
It's simple. Just pick out the button you want and copy the HTML or BBcode you see below. Paste that into your own Web pages, and if people follow it to see BYOND, that's great. Maybe they'll visit your game, or play someone else's game, or make their own game. Some may become BYOND members, and some may not. In any case, BYOND will grow, and that's a good thing for all of us.

* BYOND Wallet bonus is earned after the first 60 days of the user's membership. This bonus does not apply to gift memberships.