Not for actual search IIRC. Last time I checked, they only used their own index and crawlers for the "smart search" and instant answers. Almost all of their search results are still sourced from Bing.
That's pretty easy to check for yourself, usually whenever something does not show up on Bing it won't on DDG either. A good example of that was when the "tank man" picture disappeared from Bing and the exact same thing happened on DDG.
