True; but you can bet that Google will sooner or later try to cripple DDG. DDG would be well advised not to rely ony any search software tha is connected with Google — even open licensed Chromium.
Probably having it around is better than killing it. It isn't really a threat and it gives credibility (along with Bing) to google claiming to not be a monopoly by virtue of having competition. Crushing comparative small fry competition, on the other hand, is a bad look.