SANE configuration ... ideas?

[Modulok]

I want a scanner. I found one I like. I then checked the SANE
'Supported Scanners' list. My scanner is there:

"Perfection V300 Photo	USB	0x04b8/0x0131	good 	requires DFSG non-free
esci-interpreter-gt-f720<br>overseas version of the GT-F620"

I'm not sure what the 'requires DFSG...' business is about, but lets
get it working on FreeBSD. I followed the handbook section on
scanners. After installing a few ports and tweaking a config file
let's see if 'scanimage' knows about it:

   scanimage -L
   device `epson:libusb:/dev/usb3:/dev/ugen0' is a Epson  flatbed scanner

Yay! Let's scan something:

   scanimage -d epson:libusb:/dev/usb3:/dev/ugen0 > foo.pnm
   scanimage: rounded value of br-x from -32768 to 0
   scanimage: rounded value of br-y from -32768 to 0
   scanimage: sane_start: Invalid argument

Maybe the backend just doesn't set a reasonable defaults for
the image width/height? Let's try it manually!

   scanimage -x 640 -y 480 -d epson:libusb:/dev/usb3:/dev/ugen0 > foo.pnm
   scanimage: rounded value of br-x from 640 to -32768
   scanimage: rounded value of br-y from 480 to -32768
   scanimage: sane_start: Invalid argument

Somewhere, something is horribly wrong. Maybe it has to do with that
'requires DFSG non-free esci-interpreter-gt-f720' business. What is
that? Where do I get it and how do I use it? ... and more importantly,
how do I go about getting this scanner to work? I'm willing to read
and tweak, but I'm not sure what I'm supposed to tweak anymore.

Thanks!
-Modulok-