I have experience with routers but not Macs... I wouldn't feel guilty tapping into someone elses router if they don't have it secured.
Let me warn you, once you get that all figured out, make SURE you secure yours! I saw a thing on TV where people drive around to find these unsecured routers and download games, music and stuff and it is traced to your computer and since your router isn't secured, you can be held accountable for the illegal downloading.
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