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At the moment, I don't think there is a way to do it through the web aside from Colloquoy's plugin. All the IRC apps I've seen are native so they can only be run on 1.0.2 firmware. Using applets won't work either since iPhone doesn't yet support them though I'm not sure about CGI (Is that supported or no?).
 
Chatmosphere IRC ChatFinder

Try Chatmosphere IRC ChatFinder - It's easy to use and has a nice interface.
 
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