McObject by Roberto Zicari · Published January 1, 2009 · Updated February 16, 2014 Download an open source / evaluation copy of the Perst™ embedded database for Java or .NET. LINK
The ZooDB Object Database January 23, 2015 by Roberto Zicari · Published January 23, 2015 · Last modified May 17, 2015
Caché Post-relational Database January 1, 2010 by Roberto Zicari · Published January 1, 2010 · Last modified May 9, 2014
Eclipse Foundation: Indigo-CDO Model Repository January 1, 2011 by Roberto Zicari · Published January 1, 2011 · Last modified February 16, 2014