When a customer is just using the core activiti engine libraries(embedded, spring boot etc) with a valid license, they can enable those engines to form a cluster and monitor the health of the cluster via activiti-admin. However this feature is not documented anywhere.
Here is what you need to do to enable this.
Keep a cluster property file in each of your activiti process engine class path for it to send the stats/heartbeat back to the admin server at regular intervals. Please find attached a sample property file and a screenshot of my monitoring tab in admin when clustering is enabled.