OpenSearchServer is built on Lucene and written in Java and it can be integrated into almost any kind of application without the need to produce Java code.
Developer: Jaeksoft SarL
License: GNU General Public License version 3.0 (GPLv3)
Operating System: Macintosh, Linux, Windows
HouseSpider is an Java applet that adds indexing and search capability to your web site.
Developer: Keith L. Jackson
License: GNU General Public License (GPL)
Operating System: Platform Independent
Apache Lucene is a high-performance, full-featured text search engine library written entirely in Java.
License: Apache Software License
Operating System: Not Available