The http://www.ftdichip.com/Drivers/FT2232CDrivers.htm%3Cbr%20/%3E driver they have reccomended appear to be a USB to serial device driver, after reading through the PDF installation file on that site its bascially a way of adding a serial port to a Mac. I'm guesssing that the matrix orbital uses a similair chipset as the USB to serial adapter from that page and once installed you would have a standard serial interface to your VFD display. However at that point I think you would still have to create somthing to output data to the display over your newly created serial port.
I'm sure its possible, but its not going to be easy.

this is a link to apples example code, for controlling a serial port, its a basic command line utility, but it may give you some idea as to what you might need to to do.
http://developer.apple.com/samplecode/SerialPortSample/SerialPortSample.html

Must admit it looks past my current skill level!
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Burt
I break stuff.