I can't see any auctions in either eBay, nor Yahoo, nor any mention elsewhere about this "modified surfboard cable modem".

I've never used a cable modem, but I would imagine that the Cable Companies would at least have some level of "authentication" to allow you to tap into their neighbourhood bandwidth...no?

Maybe this is legit, but it would be nice for you to provide some further info/links/evidence that this is accurate stuff you're telling us...