This is the first time I have seen the word "foursquare" used for anything other than the game we used to play many years ago in high school.

In that game, we used tape to mark off an 8 foot square on a flat surface, and then taped the square in half in each direction to make four squares (thus the name). One player stood at each corner and when the ball (typically a volleyball) bounced into his square, he had to let it bounce exactly once and then hit into one of the other squares. If he missed, he was out and the next person in line took his place (or sometimes we kept score). Spiking wasn't allowed.

A simple fun game. I loved it. Haven't played it since high school. Now someone has even appropriated the name. Sigh.