Ah ok, you were just focused on the seasonal rewards and achievements.
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From the github page it sounds like a layered emulation running on top of the game while it's active. And yes, it is basically offline seasons, community events...
So I have been using this mod for a little while and correct me if I am wrong, but isn't the intention with the hack such that whether you play a seasonal or non-seasonal character, whatever community events you have enabled, will be active...