Unfortunately, I think you are stuck there. Unless the manufacturer writes a Linux driver, or some kind hearted soul somewhere buys the same modem as you have and writes a driver for it, it isn't supported.
To use ADSL with Linux your best bet is to sell that modem and buy an Ethernet based modem instead.
Most wholesellers should be able to sell you an ethernet modem for a good price. I got a D-Link DSL300G ethernet modem, with web interface, built in PPPoE/NAT, all manners of bridging, statistics, etc, for R750.
If I can make a recommendation though, use the modem just as an ethernet-to-ethernet-over-ATM bridge, and run a PPPoE client on your UNIX box instead, that will give you more controle over firewalling and NAT than the modem's web interface.
Willie Viljoen
Web Developer
Adaptive Web Development
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