Apache Lucene - High-performance, full-featured text search engine library written entirely in Java.
List.js - Tiny, invisible and simple, yet powerful and incredibly fast vanilla JavaScript that adds search...
Prerender - Allow your AngularJS, BackboneJS, or EmberJS apps to be crawled perfectly by search engines. View on Github.
OpenSearch - OpenSearch is a community-driven, open source search and analytics suite derived from Apache 2.0 licensed Elasticsearch 7.10.2 & Kibana 7.10.2. It consists of a search engine daemon, and a visualization and user interface, OpenSearch Dashboards.
Sphinx Search - Sphinx is an open source full text search server, designed with performance, relevance (search quality), and integration simplicity in mind. Sphinx lets you either batch index and search data stored in files, an SQL database, NoSQL storage.
AppWise - AppWise is an intelligent workspace that unifies enterprise apps into a single, searchable view.