Now that Minecraft and Mojang belong to Microsoft, things don’t bode well for multiplatfom playing or open modding and APIs within the game. That’s why plenty of players are looking for alternatives to jump ship to so they can continue enjoying their “social lego” world-building activities.
Well, good news, everyone! Alternatives exist, and at least two are open source, they work great and look beautiful.
For one there’s Minetest, the guys that signed up with Pling some months back. Minetest is aesthetically very similar to Minecraft, and although the base install gives you a very basic gameplay, the idea is that you install modules. of which there are many, to add in the functionalities (MOBs, tools, different types of blocks, and so on) you need to build your own custom environment.
Minetest is programmed in a variety of languages, with a base built on C/C++, and LUA for plugins and extensions. LUA makes programming add-ons simpler and a there is already an enormous catalogue to choose from.
Your second option is Terasology, a Minecraft clone written in Java with gorgeous looks. It works on any platform (Linux, Mac or Windows, and even within a web browser) and is, in as far as I can tell, very, very lightweight, despite the incredible visual effects and wonderful atmospheric music.
Again, Terasology can be expanded infinitely with user-developed modules. Existing modules provide such interesting modifications as procedurally generated cities, growing trees (and genetic mutations for plants), maze generators, little sentient cookie people (?) called “Oreons” (!), and… cakes! (The developers obviously enjoy their confectionary).
Both the Minetest and Terasology communities are more alive and vibrant than ever after the Minecraft debacle, and offer real fun, free and open, and blocky gameplay in amazing virtual environments.