Just wondering because I'm staying at my grandparents house for a week.
put your key on a paper, go there, download blockland ,put your key on your grandparents computer, play it, uninstall blockland then go back home
Well yeah, one at a time, just not at the same time.Or just delete key.dat.
Still fine. People are only banned if there is absolutely concrete evidence that they're sharing - and even then it usually has to be reported before action is taken. There's no automated system or routine checking that's done to deactivate shared keys.
server and client