Previously the mongodb-server required mongodb. Now it does not.
We use the mongo client from mongodb to configure the server, so we do need it even if the host is just hosting mongodb. MongoDB configuration fails by hanging forever if the mongo client is not installed.
The install script for OSE 2.0 explicitly installs mongodb at the same time as mongodb server.
The same fix was put in the OSE 1.2 script and should go in the 1.2 docs as well; for now, it's not needed, but if we were to ship a mongodb-related errata against OSE 1.2 it would likely be this newer package and the same problem would arise.
The script installs the mongodb RPM as part of the datastore component and all proceeds successfully.