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
DataNucleus provides Java data persistence to a range of datastores using JDO/JPA/REST APIs. *** Note that code development is no longer on SourceForge (code on SourceForge is for versions up to 3.3.5 only) ***