You could use a keygen to unlock full single player and LAN mode, but to play online on legit servers you'll need to have one of the keys that's stored on the master server. There are trillions of possible keys, so it is unlikely that you will generate one that is actually registered.
I guess you could play on a cracked server, but then you wouldn't be able to use the authentication system to trust or ban people. Also, you would have to join the server manually because the Blockland master server requires authentication, and the default TGE master server functionality has been removed.
Then there's the matter of updates. How many pirates keep up with the latest version of games?
Overall, it's just easier and better to buy the game.
