ComputerAssociates announced in a May 2004 that Ingress was to be made available under the CA OpenSource license (which they catchily titled the CA Trusted Open Source License).

News.com covered it : http://news.com.com/CA+open-sources+Ingres+database/2100-7344_3-5219373.html?tag=nefd.top

The source code and binary packages for Windows, Linix/x86 and Solaris/SPARC have since been made available at the project home page.

http://opensource.ca.com/projects/ingres

It is my understanding that CA wished to make their database the storage engine of choice for Zope, Plone and JBoss. I also believe that Ingres is the data engine behind the CA network management suite of applications.

I have not personally used Ingres as a database for my own applications so I can not comment on how suitable it would be as a replacement for Postgresql, MySql, Firebird or the commercial rdbms.