Firebird RDBMS offers ANSI SQL features & runs on Linux, Windows & several Unix platforms. Features excellent concurrency & performance & powerful stored procedure & trigger language.
More information and downloads at https://firebirdsql.org/, issue tracker is https://github.com/FirebirdSQL/firebird/issues
Redland is a set of object-based, modular and portable C RDF libraries providing RDF APIs for the graph, triple storage (librdf), RDF/XML parsing and serializing (Raptor), SPARQL RDF querying (Rasqal). Language APIs in Perl, PHP, Python, Ruby and others.
A collection of software to implement search engine technology. The overall search technology is built on the individual components of this project, each component is released under the BSD License, and is written in the language most suited to its task.