Actually it's not kickball, exactly. It's a variation on big-base kickbal called "Mattball". Here's a message from David Williamson:
This is going to be Epic. If you weren’t sure how you were going to spend your
Labor Day afternoon, I have solved your problem. And this is even more than a
kickball game.
Mattball is Kickball with giant
bases so that you can have multiple people all on the same base, you can run in
groups. Needless to say it’s ridiculously sweet. This is particularly
convenient if you have no idea what regular baseball rules are- you can just
watch the people around you.
So I will see every one of you on
Elbel field at 1:00pm. There is also Sand Volleyball pits if that suits your
fancy.