What would happen, I think, is this:
After the outcry and the general insanity, someone would find that they hadn't played blockland in a while and therefore it was not updated. Then they would get help from other sources to run it without the launcher. Then they'd spread the older downloads around the internet and others would join in. At first it would be single player but eventually some wiseguy would rig up a new master server, post instructions for changing the "master server" from the Disney one to the new BL one. Many users would become stuck in the process and quit in despair. Disney, seeing their customer base rapidly decreasing due to "piracy", would try to sue unsuccessfuly, and eventually it'd merge Roblox and Blockland to turn it into the biggest downfall of a virtual game in the history of the world.
Meanwhile, those of us who managed to redirect our Blockland would start trying to crack the engine, someone would eventually succeed and we'd start designing our own updates. There would be a heated debate between the "Interiors and Terrain" edition and the "Shadows and shaders" edition, until someone would point out that all the maps can be converted into formats compatible with "Shadows and Shaders" and the "Interiors and Terrain" community would slowly die out and re-join the rest of the community in a newer, brighter Blockland.