Searching for "ESXi 5.5 license keys" on GitHub typically leads to repositories containing leaked, community-shared, or "educational" keys
This is the "Gold Standard" for home labbers. VMUG is an independent community. esxi 5.5 license key github
Common Repositories: You can find lists of keys in repositories like hegdepavankumar/VMware-ESXi-License-Keys or tnader1991/VMware-Products-License-Keys. Searching for "ESXi 5
Even if you get a working key, you are running an OS from 2013. Spectre, Meltdown, and hundreds of other CPU vulnerabilities are unpatched on ESXi 5.5. A "free key" on GitHub is the least of your worries when a guest VM escapes isolation via a known CVE. esxi 5.5 license key github