But I looked at the https://help.github.com/articles/github-terms-of-service and I don't think it says you can't scrape to a database, although at least one clause about reselling or whatever causes a question.
Its cool if they are honest in their marketing and actually add something to github search, which I am pretty sure they do, because github search isn't very good.
Anyway seems very useful but don't really like the marketing.