The free license key has and is valid for ESXi 6.x versions, including 6.7. If you already obtained a free key for ESXi 6.0 or 6.5, that same key works for 6.7.
Access advanced capabilities like vMotion, High Availability (HA), and vCloud API integrations. vmware esxi 6.7 license key github
GitHub users often host lists of product keys in repositories or "Gists" for educational or homelab purposes. The free license key has and is valid for ESXi 6