regain is a fast search engine on top of Jakarta-Lucene. It crawles through files or webpages using a plugin architecture of preparators for several file formats and data sources. Search requests are handled via browser based user interface using Java server pages. ´regain´ is released under LGPL and comes in two versions: 1. standalone desktop search program including crawler and http-server 2. server based installation providing full text searching functionality for a website or intranet fileserver using XML configuration files.
Platform: Windows, Linux;License: LGPL
Reference: https://regain.sourceforge.net/