When you download Fusion Server, it comes with a 30-day trial license. Contact Lucidworks to obtain a permanent license.
Fusion Server provides a license management UI and a license API for installing and managing licenses. When you upload a license, Fusion Server stores it in ZooKeeper, so you only need to upload it to one node per cluster.
The Fusion UI notifies you when your trial license is about to expire. When your license has expired, Fusion Server accepts no configuration changes until you upload a valid license.