If active/active is used than you need two licenses each for one active node.
But you have to do the backup trough cluster host.
If you don't than index will be written under the physical host, configuration with DSN for LAN free will not work.
Configure new client for each cluster host on NW.
curphyhost is short for current physical host.
In that way (if you put curphyhost)when failover occurs for cluster host from one physical host to the other your LAN free backup will work without intervention.