I've updated my iPAQ with Familiar 0.8.4 by reflashing and tried again to connect thru USB and IT WORKS !!!!!!!!
I was right, the driver used on iPAQ is the usb-eth and not the g_ether like it was ativated befor the update.
So, on Familiar, everything is good OUT OF THE BOX.
Thanks a lot to you the dev of AJZaurus for the driver that make me a iPAQ/Linux owner happy