Well.. hah I just got my AIW card to capture under linux. Happens to be a AIW 7500 but the same work should apply in your circumstance.
There is a well wriiten HOWTO at this link
http://www.reades.com/radeon.html
It breaks down to going to the gatos.sourceforge.net website and installing modified ati drivers for xfree called "ati.2", installing avview, and then install the 'km' module.
I will give a word of caution the latest release of the "km" module is kernel 2.4.xx specific and will not work with a 2.6 series kernel. The latest cvs snapshot worked for me using 2.6.5 with a few minor adjustments to km.c and km_api.c and following the directions in the README!
Without the km module you can still watch TV in your linux box, just not capture it.
If you need I'll post the changes I made.
-Ian