yes, there's a lot of misconceptions here on hn about what DDG actually is. Indexing the web, now, is beyond the capabilities and budget of individuals, you need the resources and backing of a company like google, ibm or microsoft to do so. DDG is federated search, not a search engine. While they might crawl a few sites, it's Bing that you're seeing in the result, the work of Microsoft engineers (along with any remaining PowerSet guys.)
From a thread on DDG's community site DDG uses Yahoo Boss (not sure if that's Bing powered now) but I would bet anything it can fall over to Bing without too many issues. It came up during a discussion of the new Bing pricing which should come into affect in 2 days or so. DDG does crawl some things directly as well (DuckDuckBot) but its nowhere close to the scope of Bing/Google. DDG also does meta searchs using API's such has,
The top zero click result is from other sources on the web (disclosure the last one comes from my site).
The only search engine I have found which gets close to this is VerticalSet although with the new Bing pricing I am not sure how long it will exist for now.
Yahoo already uses Bing.