No, Blockland can not be "hacked" through in-game features such as events or whatnot, as that is part of the game.
Yes, Blockland can be hacked outside the game. Just because something is "well-coded" doesn't mean it's hack-proof. However, I'm sure very few, if any, blockland players possess that ability, and I'm sure even fewer of them are actually going to take the time to use it.
In short, don't worry about it. Ban people that claim they know how and/or griefing, then move on with life.