From Hans-Gerd we have the following information: 

You can update your howto for this Card and report rhel4 as working distribution. The only thing to know additional to your
howto is that redhat does not load usbserial by default, but you can use /etc/rc.modules to do that. Create the file which does
not exist by default an add the following line:
modprobe usbserial >/dev/null 2>&1
For our we need this in /etc/modprobe.conf:
options usbserial vendor=0xaf0 product=0x6300
and that's it.