I've set up an EV installation with Microsoft Cluster and the license is not an issue as only one is active at a time anyway and it is really based on users in the organization. I.E. you can have multiple EV servers running different tasks and split them using building blocks without having to buy lots of licenses becuase it is a performance thing and the # users and features they can use doesn't really change.
There is a cluster guide for setting up EV. There are some things to be careful of with shared storage such as making sure the Message Queues can be accessed by the active node at any time.
But otherwise it works alright. Some manual configuration might be required. I would probably recommend to use shared storage on a CIFS share from a NAS/SAN disk. This way the cluster just acts like another EV Server Node.
But in my opinion, I would rather use building blocks than clustering for EV. You might want a clustered SQL Database! but otherwise not so much...
