Free Software for your own Search Engine, Explorer for Discovery of large document collections, Media Monitoring, Text Analytics, Document Analysis & Text Mining platform based on Apache Solr or Elasticsearch open-source enterprise-search and Open Standards for Linked Data, Semantic Web & Linked Open Data integration.
Usage tutorial here: https://www.opensemanticsearch.org/doc/tutorial
Github: https://github.com/opensemanticsearch
Of course it has an API: https://www.opensemanticsearch.org/doc/admin/rest-api