It works, it activates, and Windows will say it's genuine if you ever reinstall windows from scratch on that machine but technically you don't have a valid license for Windows 10. It's a complete non-issue for personal use and Microsoft is blatantly still allowing the upgrade process and issuing digital entitlements, but for a business this would cause you to fail an audit and need to pay up to license Windows 10. Basically it's a free upgrade for home users but no different than pirating Windows for businesses.