The gnustep-db supports a pluggable database backend mechanism. The OGo source distribution comes with database adaptors for PostgreSQL and FrontBase, Sybase and Oracle adaptors are part of the commercial SKYRiX 5 distribution and not part of the OGo sources.
We at OGo are open to the contribution of additional database backend adaptors, but having support for a perfectly suitable OpenSource database, PostgreSQL, we see no immediate need to extend OGo for MySQL or other database on our own.