I just now tested the DMZ host configuration on my BEFW11S4, and it does forward connections to my laptop on the wireless. I tested with port 22 (ssh). It does not work with port 80, but I think that's because my provider blocks inbound connections on port 80.

Maybe you should forget about the DMZ host and the built-in router/NAT in the BEFW11S4 for now. Can you get the Airport card in your G4 to talk to the Linksys?

One other thing: I cannot test it right now, but it looks like you can set the BEFW11S4 to operate as a router rather than a gateway on the "Dynamic Routing" tab in the configuration utility.

[link|ftp://ftp.linksys.com/pub/manuals/befw11s4_ug.pdf|ftp://ftp.linksys.co...s/befw11s4_ug.pdf]