You would have to have the Debian OS installed on the side, which has been discussed on the forum many times. And then you'd have to run it on Debian. After hooking up the phones WiFi to Debian, which as far as I know, there aren't any Drivers made yet.
So, the G1 is capable, but it takes a great deal of work.
Not even mentioning the fact that it is illegal to crack the WiFi codes in some places...
Also, this is not a development question, it should be in Dream Q&A.