There's no denying that Minecraft is a favorite game to millions. And being written in Java enables it to run on a variety of platforms, including Linux. With a huge modding community, there are countless Minecraft tinkerers out there who would love to be able to get under the hood and play around with the source code themselves. Unfortunately, the source is not available to the general public.
But there's good news. Minecraft's popularity has led to many attempts to recreate the game, and others in a similar vein, as open source software. Interested in a free Minecraft alternative? Here's a quick look at some of clones and derivatives out there that you really ought to check out.
These projects are in widely varying levels of completion, and serve a number of different goals. Some seek to duplicate the Minecraft experience completely, or to at least provide a very similar experience. Others are taking the voxel-based gaming concept in entirely new directions, and still others are really more of a framework to help you build your own game or creation.
The first game on our list is Minetest. Minetest is perhaps the most complete alternative to Minecraft, which is billed as a "near-infinite-world block sandbox game and a game engine." It supports multiplayer games and subgames, features a number of terrain generators, and a number of different default biomes. It also features a very user-friendly API for creating mods in Lua.
Minetest is open source under the LGPL, and is written primarily in C++ so it's fairly fast compared to some others written in scripting languages. Minetest runs on Windows, OS X, Linux, Android, FreeBSD, and possibly other operating systems as well. Check out the source code on GitHub.
Terasology might win the award for the most beautiful rendering engine in the pack; its shadows are both ominous and spectacular. What started out as an experiment in procedural terrain generation has turned into a full-featured game, complete with multiplayer and a number of addon modules installed by default to let you try out different gameplay mechanics.
Terasology is written in Java, and is made available under an Apache 2.0 license. Because of it's Java-based system, it ought to run on just about any platform with sufficient power so long as you have a Java 8 virtual machine installed.
Voxel.js is put together as a number of related projects, meaning you can use as much or as little of the code as you wish when you craft your perfect game. The main library, voxel-engine, is a fairly basic engine for rendering boxy scenes, but there are over 200 additional addons available. Check out the gallery for some ideas of what others have built with the engine. The main engine is released under a BSD-style license; other addons may be licensed differently, so it's worth checking before you make assumptions.
TrueCraft is written to be very close to the original game, and is described as a Minecraft "implementation," as opposed to a clone, and is compatible with official Minecraft server releases. The author of TrueCraft seeks to implement beta version 1.7.3 of the original game, a time in the game's development he deems "nearly perfect." A snapshot intentionally frozen in time, TrueCraft seeks feature-parity with Minecraft.
Because it is so close to the original, TrueCraft has taken great pains to avoid copyright issues by only allowing code from developers who have not decompiled or otherwise had access to the original game's source code, though those who have are welcome to contribute in other ways. TrueCraft is written in C# and is open source under an MIT license.
Craft is another open source voxel engine in the style of Minecraft. Its simplicity may appeal to you if you've interested in building a game similar to Minecraft but aren't sure where to start: the game engine resides in just a few thousand lines of c code and uses OpenGL for rendering. It uses simple algorithms for terrain generation and other tasks, and everything is stored in an sqlite3 database. There's also a Python-based multiplayer server which is worth giving a try.
Craft is made available under an MIT license.
Other great options
Some other notable mentions which you should give a try:
- TechCraft is another Minecraft-style engine written in C# using XNA 4.0, and is open source under a Microsoft Public License. It was written to support a game called Xenogalaxies, but is used by other projects as well.
- Manic Digger is another take on the voxel game engine, written in the C# and Ć programming lanuguages, and is released under an Unlicense. Manic Digger supports numerous gameplay modes include a first person shooter implementation.
- Freeminer is another sandbox game inspired by Minecraft, and based on Minetest. As a fork, the authors seek to "make the game fun while trading off some bits of perfectionism."
- The final two picks are open source alternatives to the Minecraft server, OpenCraft and Glowstone. OpenCraft seeks priimarily to add scripting capabilities and griefing-prevention to the standard Minecraft server, while Glowstone's focus is on being lightweight and maintaining a mature API. There are many other options for you to consider beyond these as well, a partial list of which is available here.
And there you have it. This list is far from comprehensive; there are many other options out there just waiting for you to explore, and as time goes on we'll undoubtedly see more choices emerge as enthusiasts fork these games or strike out on their own. Which one is your favorite, and which one did we leave off that you wish we had covered?