Startpage.com is the one I use day to day (I work at the company that owns it). They use straight Google results through a proxy in their own data centers, it's anonymized before it hits anything
I'm also very interested in the details. According to their website they are paying Google to provide them with the results. But the revenue streams to startpage are not provided on their homepage (or at least I haven't found them yet).
Edit: https://support.startpage.com/index.php?/Knowledgebase/Artic... This gives additional information. Apparently they are showing ads that are only related to the search terms. I guess they are showing more ads than Google? Otherwise this wouldn't really make sense. Or maybe individualized advertisements in the search results aren't that much of a big money-maker for Google (!)
It's the same amount of ads. The hyper targeting Google does is incredibly profitable because of the scale they operate at. If you make the click through rate of an ad even 0.1% better over billions of searches it more than pays for the R&D of an engineering team.
Really the only way to compete against Google from a feature perspective is the privacy angle. You're sacrificing better click through rates to target a market that cares about privacy. Making something private requires a lot less engineering and product power than hyper optimizing tracking. By definition if you're not doing any tracking you don't need to employee people to set up tracking systems.
The deal is 15+ years old. To my knowledge it was made back when Google was still a very young company. There's a surprising amount of legacy contracts from Google/Bing/Yahoo floating around that power all of these search engines (Ecosia, DDG, etc).
