There is Minetest, which has at least one configuration that attempts to mimic vanilla Minecraft, but I'm not certain how accurate it is. The stored data struc

There is Minetest, which has at least one configuration that attempts to mimic vanilla Minecraft, but I'm not certain how accurate it is. The stored data structures are well understood for both versions. See for example https://www.amuletmc.com/ https://www.amuletmc.com/ (Editor, Python) or https://github.com/df-mc/dragonfly/tree/master/server/world/mcdb https://github.com/df-mc/dragonfly/tree/master/server/world/... (Code, Go)