Excellent question - I do not know the answer.

I just assumed not given their no tracking/personal info policy. But since you asked I did some searching and found posts where DDG are saying they do not censor results.

While researching this answer I found this interesting article How to Live Without Google

But we know Google does via YouTube as explained in Who Will Google Silence Next?.

Plus Google's selective "Fact Checking" within search results is another form of censorship.

I have not observed either of these practices on DuckDuckGo