db4o ("database for objects") was an embeddable open-source object DBMS for Java and .NET environment.
Embedded
Object-Oriented
http://www.db4o.com/
https://github.com/pegurnee/db4o
db4objects Inc.
US
2000
2014
Versant Corporation
Commercial, Open Source
All OS with Java VM, Windows
GPL v2, Proprietary
https://en.wikipedia.org/wiki/Db4o