YaCy is a free search engine that anyone can use to build search the internet (www and ftp) or to create a search portal for others (internet or intranet). The scale of YaCy is limited only by the number of users and can index billions of web pages. In p2p mode it is fully decentralized, all users of the search engine network are equal and it is not possible for anyone to censor the content of the distributed index.
Google() meets the Matrix. Red Piranha combines Lucene (Searching Ability), XML-RDF (ability to learn), Tomcat (for P2P Power) and Spring (Ease of use) to not only let you find anything, anywhere, but to actually understand what you are looking for.