I would imagine that they'll send the appropriate gerber files off to their choice of board manufacturer to have them built.  BKKCoins open sourced this, he's not the exclusive supplier of boards - anyone can have the PCB's made.  The K-64 is just three additional cut-and-pastes of the K-16 with the proper spacing between the copies.  Theoretically you could saw the K-64 board up into four separate K-16s (although if I were doing it, I'd tie the Vcc and GNDs together across the boards and eliminate the redundant power connectors at the very least.)