Looks very similar to Minetest (https://www.minetest.net/) (Edit: but this is nonfree and hasn’t yet been ported to GNU/Linux, while Minetest has and also works on 3 BSDs). Although Minetest does not include built in tools for asset creation — most models, textures, and scripts seem to be made in Blender, GIMP, and standard text editors — there is a mod to convert in-game builds into models (edit: including textures in the future: https://content.minetest.net/packages/random_geek/meshport/ / https://github.com/random-geek/meshport) and mesecons’s (https://mesecons.net/) Luacontroller block allows you to type and run Lua in-game without restarting.