I fumbled my way through getting it to work on both. I've reverted back to the sharp rom for now though, as it does everything I need.
In opie, set the wireless interface to come up automatically in the gui, reboot, then there should be all the options to set it up available within the gui, including scanning for APs.
In gpe, as root type "ifup wlan0" and then you should be able to get it to work from the gui. You will need to bring the interface up each time you reboot your zaurus.
I was not able to get WEP working with either of them, which was the biggest reason I have for going back to the sharp rom. I also had a lot of problems with suspend not functioning properly.
There are some more threads about this in the openzaurus forum, so if this doesn't help, you can check there.