The List of Open Source MineCrafts

MineCraft will be open source someday in the future (http://www.minecraft.net/about.jsp):
"Once sales start dying and a minimum time has passed, I will release the game source code as some kind of open source. I'm not very happy with the draconian nature of (L)GPL, nor do I believe the other licenses have much merit other than to boost the egos of the original authors, so I might just possibly release it all as public domain. "

But for now, enjoy this list of open source MineCraft alternatives!

1. Manicdigger
http://sourceforge.net/projects/manicdigger/
http://manicdigger.sourceforge.net/news/
"Manic Digger is a public domain 3d block-building game similar to Minecraft."
Features: Infinite world, Rails, Crafting, Shadows, Multiplayer
License: Public Domain
Language: C#





2. Opencraft: http://opencraft.sourceforge.net
OpenCraft is an alternative Minecraft server, providing more advanced features than the official distribution.
Features: Scripting, griefing preventation
License: BSD
Language: Java


3. Minedroid: http://code.google.com/p/minedroid/
Features: Work with a touchscreen interface
License: New BSD
Language: Java


4. Infiniminer: http://thesiteformerlyknownas.zachtronicsindustries.com/?p=713
https://github.com/krispykrem/Infiniminer
http://code.google.com/p/infiniminer/
Features: multiplayer
License: MIT
Language: C#


5. Minetest-c55:
http://celeron.55.lt/~celeron55/minetest/index.php
Features: Survival mode, creative mode, multiplayer, dynamic lighting, almost infinite world, Infinite map generator
License: GPL
Language: C++


6. TechCraft: http://techcraft.codeplex.com/
Features: Minecraft style terrain engine
License: Ms-PL
Language: C#


7. ArdorCraft: http://ardorlabs.se/ArdorCraft/
https://code.google.com/p/ardorcraft-api-examples/
https://github.com/rherlitz/ArdorCraft
Features: API to build new types of blockworld games
License: MIT
Language: Java


8. Terasology (Blockmania):
http://blog.movingblocks.net/blockmania/
https://github.com/MovingBlocks/Terasology
Features: Procedural terrain generation, efficient rendering
License: Apache 2.0
Language: Java



Finally, this one is not open source, but you can't miss it!
http://ace-spades.com/ http://buildandshoot.com/(based on voxlap engine)
"It's the best bits of Minecraft crossed with the fast-paced shooter gameplay of Team Fortress."
Features: Dynamic lighting, 32 players battling, CTF or Territory Control game modes
License: Closed Source
Language: C/C++

Ace of Spades is now a commercial game, but we have

9. Iceball: Open Source Version of Ace of Spades!

https://github.com/iamgreaser/buldthensnip
http://buildandshoot.com/viewtopic.php?f=5&t=60
http://iceballga.me/index.php


10. Minecraft in Blender: Minecraft like in the Blender Game Engine.
http://www.youtube.com/watch?v=bCJa5H-oOxc&feature=player_embedded
www.blendernation.com/2013/03/19/minecraft-in-blender/
 

More:

Crafty (C++)

http://www.sea-of-memes.com/downloads/Crafty.html

Craft (C)
https://github.com/fogleman/Craft

Voxel.js (JavaScript, BSD)

http://voxeljs.com/

Voxeliq (C#)
https://github.com/raistlinthewiz/voxeliq

Blackvoxel (C/C++, GNU GPL V3)
http://blackvoxel.com 

CraftSaga (Unity, C++)
https://github.com/komorra/CraftSaga  

Links:
AIR-based Minecraft Map Viewer (with source code):
http://www.joranderaaff.nl/2011/10/minecraft-map-viewer/

Minecraft like games in flash:
http://kube.en.muxxu.com/
http://galaxy55.com/

A minecraft level render in flash:
http://liquify.eu/flash/MCExplorer
http://www.minecraftforum.net/viewtopic.php?f=25&t=96591
Source Code of MCExplorer (open source minecraft map render/viewer in flash/as3):
https://bitbucket.org/SmilyOrg/mcexplorer/wiki/Home

Minecraft and WebGL:
http://metaphysicaldeveloper.wordpress.com/2011/12/20/implementing-minecraft-in-webgl/
https://www.shadertoy.com/view/MdlGz4

Minecraft4kAS: http://wonderfl.net/c/sqL5
Minecraft4kJS:
http://jsdo.it/notch/dB1E
http://jsfiddle.net/uzMPU/

Minecraft4k(Java):
http://www.mojang.com/notch/j4k/minecraft4k/
http://pastebin.com/XK4EExyg

Minicraft(update on 2013/11/15, html5 in 252 bytes with source code):
http://www.p01.org/releases/minicraft/

https://github.com/fogleman/Minecraft (Minecraft in 900 lines of Python)
https://github.com/boskee/Minecraft
https://www.slideshare.net/rdonkin/pyglet-and-minecraft-v1-1

Others:
http://www.octaforge.org/
http://sauerbraten.org/
http://www.sandboxgamemaker.com/

http://alternativeto.net/software/minecraft/
http://gameslikefinder.com/games-like-minecraft/(Thanks to Samuel Taylor)
https://bitbucket.org/volumesoffun/voxeliens (retro-style arcade shooter)