Just because you don't like the interface, does not give you license to steal their data. I think HN is fairly ugly, but that doesn't mean I have a right to scrape the site in order to reproduce a slightly better looking, for-profit clone. At least not without PG's express permission.
Yahoo search would be a hell of a lot better if they could just scrape results from Google, but thankfully they lack the misguided sense of entitlement that Padmapper seems to suffer from.
You actually do under the HN terms of use, which are permissive in the licenses they grant regarding HN posts. For example, see HN Magazine and various other HN-based sites and services.
But as you note, the important thing here is the "license." Craigslist offers paid licenses to app develoeprs, which PadMapper chose not to pay for.
Yahoo search would be a hell of a lot better if they could just scrape results from Google, but thankfully they lack the misguided sense of entitlement that Padmapper seems to suffer from.