The Xapian Project - Open source search engine library written in C++, with bindings to allow use from other languages as well. DataparkSearch Engine Tool - Open source search engine tool released under GPL and designed to organize search within a website, group of websites, intranet or local system. KDE GUISearch - A tool for finding code by looking at the applications' GUI text messages (e.g., "Undo") and returning associated callbacks/slots (e.g., slotUndo()). Allows searching the KDE project CVS repository as a live demonstration. Egothor - A cross-platform, full-featured text search engine written entirely in Java. It can be configured as a standalone engine, metasearcher, peer-to-peer HUB or used as a class library. BDDBot - A web robot, search engine and web server written in Java and available under GPL. Includes related resources. [Project no longer actively updated] OpenWebSpider - An open source web spider and search engine. Includes demo, source code and screenshots. Sphider - A lightweight search engine in PHP. Includes details of features, documentation, support forum, and download. [GPL] Locust - Specifically designed for knowledge area or corporate search, written in C++. Arachnode.net - A .NET web crawler written in C# using SQL 2005 and Lucene. Documentation and online demonstration. YaCy - A distributed Web crawler and caching HTTP/HTTPS proxy built on the principles of peer-to-peer (P2P) networks. Nutch - Effort to implement a prototype of an open source web-search engine. Grub - Open source, cross-platform distributed crawler. FAQ, documentation and a support forum. Yioop! - A PHP, GPLv3 search engine designed to do open web or intranet crawls. Wumpus - A C++, GPL-licensed search engine developed at the University of Waterloo. Wumpus allows control of the text unit retrieved based on structural constraints in the query. Indri - A cross-platform search engine written in C++ that provides text search and a rich structured query language. BSD-like license. Sphinx - A search engine designed for indexing database content. It natively supports MySQL, PostgreSQL, and XML pipe interfaces. It is written in C++ and has a GPL license. CSIRO Arch Intranet Search Engine - An open source, high precision corporate search engine based on Apache Nutch Groonga - An LGPL 2.1, open-source, fulltext search engine and column store written in C. Works with MySQL and Postgres. Site provides online documentation and downloads. OpenSearchServer - A GPLv3 search engine and crawler for urls, databases, and file systems. Comes with an XML/HTTP API, PHP/ASP client. Based on Apache Tomcat, Java Server Faces and JBoss RichFaces. Norconex HTTP Collector - Java-based Apache licensed enterprise web crawler running on any platform, and integrating with virtually any search engines (open-source or commercial). Strus - A collection of C++ (C++98) libraries and command line tools for building a competitive full-text search engine. Development status is pre-alpha. Datafari - open source enterprise search solution - A packaged, Apache v2-licensed, enterprise search solution that leverages ManifoldCF for data sources, Solr for the search engine, and Cassandra for user management.