If you FTP into the router you can see the guts of it - hack around the builtin http server etc.
Based on the Conexant AccessRunnerADSLModem chipset.
I just got this ADSL modem/router working, with Fedora Core 3. I did not use the USB port at all.
Default router setup address: 10.0.0.2, username "admin", password "epicrouter".
I could not get firefox browser in Linux to access the router set-up, I don't know why. Used IE in Windows to set it up (just enter 10.0.0.2 as the URL).
Once you access the browser setup screen, go to the WAN configuration, press "Select" for Pvc0, and you'll see the screen where you must enter the username/password supplied by your ISP, on the right. That's the only thing I had to change from factory defaults. There are some similar setup choices in the PPP configuration setup area, but that didn't work (for me). The setup screens for this router are not obvious, and the manual is crap!