The majority of results still comes from Bing:

> 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...

Note that their own crawler is only mentioned in the context of Instant Answers so it doesn't seem it's actually used for any regular search results.