DuckDuckGo's results are a compilation of "over 400" sources,[8] including Yahoo! Search BOSS, Wolfram Alpha, Bing, Yandex, its own web crawler (the DuckDuckBot) and others.[3][8][9][10] It also uses data from crowdsourced sites, including Wikipedia, to populate knowledge panel boxes to the right of the results.[10][11]
The Wikipedia article makes it sound like their search results are from "over 400" sources and their own bot. That's just for the widgets and Instant Answers.
Their own Sources page makes this distinction more clear:
"To do that, DuckDuckGo gets its results from over four hundred sources. These include hundreds of vertical sources delivering niche Instant Answers, DuckDuckBot (our crawler) and crowd-sourced sites (like Wikipedia, stored in our answer indexes). We also of course have more traditional links in the search results, which we also source from multiple partners, though most commonly from Bing (and none from Google)."
