VMware provides a free version of the ESXi hypervisor. Acquiring a free license only requires creating an account in the VMware Download Center. Once you are logged in to their portal, you have access to a free license key to use ESXi indefinitely on a single server.
VMware also provides binaries for installing ESXi, but those are not necessary at MacStadium as we pre-install ESXi on a hosted Mac with a 60-day trial license before providing you access. You simply have to apply the license key acquired from the VMware Download Center to your ESXi installation.
It's important to clarify that this only applies for our dedicated Mac servers. It cannot be used with our hosted Mac private cloud solutions. The free license has restrictions that make it incompatible with a cluster of servers and the necessary additional VMware software we install for management and automation.