Oddbean new post about login | logout To be fair, even DuckDuckGo is closed-source. The only fully open-source search engines I know of are wiby.me and YaCy.
There is also https://stract.com/
I took a brief look at it and it looks good. Do you know if it does its own indexing or if it uses something else like Bing in the background?
Wow, this looks amazing. https://stract.com/search?q=site%3Anjump.me+pablo
There is https://html.duckduckgo.com and they have onion addresses as well, which is a good solution for the client-side but of course the engine itself is not free. Just heard about stract from this thread, there is also https://metager.org/
The neat thing about YaCy is that the index is distributed peer-to-peer.