While this may work (both computers may be able to see the interface at the same time), it is not advisable for a number of reasons.
1. Because the interface is controlled by its drivers on a computer, having another computer try to control it all the same can cause problems.
2. In initial testing, if one computer has a crash or other problems, the other computer may fail too.
3. The second port on MOTU Firewire interfaces was designed for Firewire peripherals like hard drives. It was not designed to be connected to two computers.