>The problem with minetest is nobody mods it so you can't program a turtle in LUA on minetest, only minecraft.

Minetest has quite a lot of mods, admittedly - I even made a few. The problem with Minetest is that it has too many modders and not enough players. The problem with Minetest is that the voxel engine zone itself is fragmented: Minetest itself has three different maintained versions, and there's other clones like Terasology as well. The problem with Minetest is that the APIs are and will probably remain too limited for the most complex things, seeing as it's not the kind of modding where you turn the engine inside out for fun and it happens to work with most mods for some reason - and, even then, there's far too few developers on Minetest's core engine and far too many opened/unmaintained pull requests.