Yes ! The gnustep-db supports a pluggable database backend mechanism.
The sources are coming with example adaptors for
<a href="http://www.postgresql.com/" target="extlink">PostgreSQL</a>
and
<a href="http://www.frontbase.com/" target="extlink">FrontBase</a>.
<br /><br />
The major requirements for an OGo database are that it supports proper
transactions and database constraints.