The module can be configured in several ways, I set mine up to use synchronous communications on port A and asynchronous on port B. I also set the module to be externally powered. If you can find a suitable connector, you can make a completely external converter cable, in this case you will probably want to configure the module as bus-powered as the 5V output from the link port is reportedly rather poor.
This software is written for the chip's synchronous serial transfer mode, which offers transfer rates of up to 110KB/s. If you have another fast transfer method available you may want to use asynchronous communications on both channels. The synchronous mode is trickier to program for, and using virtual comm port drivers any terminal app could be used to communicate with the Saturn. Other programs which communicate over the serial port (eg. GDB) could be used without modification.
The transfer tool uses libusb and libftdi.
OS X users can get libusb via e.g. Fink. This code is released under the GNU General Public License.
The Saturn client code is released into the Public Domain.