This article may also be of interest to you:
https://duck.co/help/company/yahoo-partn...
In short, DDG will continue to work and function as it has in the past, while continuing to improve. DDG has always used Yahoo as one of it's sources, they have just strengthened the relationship with them for improved feature (date filtering, for example). DDG uses it's own search algorithms and is NOT Yahoo in a DDG wrapper.