Similar to DDG, Startpage provides results in a privacy respecting way, but it uses Google instead of Bing (and Oath), which DDG uses. There’s a common misconception amongst some that using !g on DDG is private, but it’s just a redirect, so Google can gather information from that search. Using !s as the fallback instead will keep your searches private.
So that means either Startpage has higher ad margins than Google or Google is selling services to Startpage below their own search margins or Startpage has some other source of funds to subsidise the search engine.
I have no idea how much revenue this may bring in but it can't be much since I don't think I've ever seen it recommended in an Ask HN thread.
I expect this is the case - it's still better for Google to capture a user at lower margins via Startpage than to lose them to Bing.
I do find the mention of DDG using Oath rather alarming, though, since Oath seems particularly obnoxious, at least with their GDPR pop-up on Tumblr. What does DDG do with Oath?
DDG was originally using Yahoo and Bing. Yahoo was thrown under the Oath umbrella along with AOL, Tumblr, Engadget, etc. when they were acquired by Verizon. I assume for transparency, DDG stated they use "Oath (formerly Yahoo) and Bing" on their Sources help page to indicate who they're actually making the deal with.[0] However, I guess Verizon has changed the Oath name to Verizon Media, so now it's "Verizon Media (formerly Yahoo) and Bing".
But, to answer your question. It's just a long winded way of saying Yahoo.
[0]: https://help.duckduckgo.com/duckduckgo-help-pages/results/so...
DDG is at least a reasonable way to ween yourself off Google search rather than needing to go full cold turkey.