I've recently gotten into using DuckDuckGo as my main search engine. Looking at DDG, and others, I started to wonder:

Are there any community driven, open source, search engines currently running?

After doing some searching, I couldn't find any. This struck me as odd considering there are number of initiatives out there from mapping (OpenStreetMaps) to music (Open Music Archive) to human knowledge (Wikipedia).

Does this exist? And if not, why not? Is there any appetite for such a project?