Each server will need their own activation license for the Call Bridge, same applies to Recording and Branding if used.
Each server will also need their own call licenses, but you can install them on both servers, this is done by simply specifying the MAC address of interface a from each server when claiming the Multiparty licenses. You'll then get a license file for both servers that includes the quantity of Multiparty licenses you claimed.
You should not run a 2 node cluster, this is because if a database or XMPP server goes down, the remaining node won't be able to promote itself to master and the cluster will not function. A 3 node cluster is recommended for resiliency, the third node that runs the redundant database and XMPP server simply needs an activated Call Bridge so the XMPP server can be enabled.
Recommend you take a look at the CMS Scalable and Resilient Meeting Server Deployments.
