Hi Jacob,
You will need a license for each node of your cluster. For example, if you had 6 nodes but only 4 floating licenses, then only 4 nodes would be able to run/process at the same time.
As far as I know you will also need a license for your server that controls all nodes of your cluster, which means that you need a minimum of 3 licenses to gain any computational advantage (2 nodes + 1 server). No license needed for server, as mentioned by Alexey.
Regards,
SAV