To avoid confusion, ignore all above posts.
If you know what LAN is, read:
You can only use the same key on the same network, however the name must not be changed.
If you don't know what LAN is, read:
Your network is any computer connected to the same router. Only the computers connected to that router may use the same key at the same time. You cannot change the name.
Also read:
If any key is being used at two different IPs, regardless of what server you're in, the first one to put it in will get disconnected, and if that one is hosting a server, that server will go down without the ability to save. If it happens too often, the entire key will get disabled and unable to be used ever.
Final note:
Don't share keys.