You may be missreading the Disclaimer.

I believe hte comment about commercial use is in terms of posting info on the site (ie: using hte message boards to sell stuff) ... if you wnated to use their address lookup form for commercial purposes (which is what Scrape::USPS::ZipLookup does) that should fall under their "To reproduce, republish, upload, post, transmit, distribute or publicly display material from this website you will need written permission from the Postal Service." clause.

Getting permission may be hard, but it's not impossible.