The purpose of the restore only client is that it is useful when there is a requirement to restore data to another device other than the machine the production data / backups are on. This allows data to be restored without affecting production backups or production systems.
To implement the restore only client on a device run the Backup Plus installer and reconnect to an existing account. You can do this by clicking the "Install Restore-only" button on the dialog box which appears after the "Security code" step during the installation process:
When the client is launched after the installation, only restore functionality will be available.