Apache Jena, A free and open source Java framework for building Semantic Web and Linked Data applications.

Blazegraph High Performance Graph Database

Ontop is a platform to query relational databases as Virtual RDF Knowledge Graphs using SPARQL

INCEpTION provides a semantic annotation platform offering intelligent annotation assistance and knowledge management.

Information Integration Tool

A KBQA system based on DBpedia.

Eclipse RDF4J: scalable RDF for Java

SPARQL Anything is a system for Semantic Web re-engineering that allows users to ... query anything with SPARQL.

GraphQL interface for querying and serving linked data on the Web.

OpenStreetMap for the Semantic Web

An RDF plugin for Solr

Software platform implementing and extending the standards of the Semantic Web.

HDT Java library and tools.

Streaming generic JSON to RDF converter

A highly scalable RDF triple store with full-text and GeoSPARQL support

SKOS-Play allows to print SKOS files in HTML or PDF. It also embeds xls2rdf to generate RDF from Excel.

Java client for the MarkLogic enterprise NoSQL database

Ontology-driven Linked Data processor and server for SPARQL backends. Apache License.

Streaming, transforming, SPARQL-based CSV to RDF converter. Apache license.

RDF2X converts big RDF datasets to the relational database model, CSV, JSON and ElasticSearch.