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)."

https://help.duckduckgo.com/duckduckgo-help-pages/results/so...

It's interesting that they write "none from Google". Because you never know, Bing might be copying some search results from Google in turn [0] ;).

[0] : https://www.wired.com/2011/02/bing-copies-google/