I'm developing in my spare time a game like Minecraft. In fact, it isn't "like Minecraft", because I'm trying to make it a close as possible copy of it (meant as exercise for myself at the age of 16 and simply because of it is fun to me). Of course, I'm not copying the code using the Minecraft Coder Pack (MCP). I started the game from scratch in Java using OpenGL.

So, my question is: am I allowed to put my source code online on a public source code versioning host like GitHub, Google Code, et cetera (which makes my code open source, because I don't want to pay to use a private host)? Of course, I don't want to sell the game, because the game is from Notch.

A detail which might be important is that I'm using a custom texture pack (so, not the one that is shipped with the real Minecraft).

If it is allowed, are there any rules? I took a look to this page, but it seems that he doesn't say anything about this: http://www.minecraft.net/terms

Edit: There is the game called Terasology (started under the name Blockmania) from Begla. That is a nice project, but it is not meant to be as close as possible to Minecraft. That project is open source.

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    \$\begingroup\$ As long as you aren't violating anybody's copyright, you are likely fine (though I'm not a lawyer, et cetera). You could even sell the resulting game. However, you have to consider both Mojang's copyright and the copyright of the author of the texture pack you're using -- you can't distribute (or profit from) that either, unless the author has granted you that right. \$\endgroup\$ – Josh Jan 11 '12 at 16:30

Okay, so here is my understanding of this - coming from developing games and a constant attempt to obtain more knowledge on licensing, copyright, open-source projects, etc.

You are allowed to make a Minecraft clone and open-source it with no repercussions as long as you don't use the title Minecraft, don't use any of Minecraft's source code, and don't use any of Minecraft's assets.

Doing any of those will violate the game's copyright. Programming a game to reflect a game you really enjoy isn't at all a bad thing, and sharing that code is a good thing. However, stepping on any of the toes of those at Mojang by using code or assets they created is not okay.

  • \$\begingroup\$ How do you interpret the assets? \$\endgroup\$ – Martijn Courteaux Jan 11 '12 at 16:09
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    \$\begingroup\$ The assets would be any audio, models, code, and art that Mojang created. \$\endgroup\$ – Brett Chalupa Jan 11 '12 at 16:11
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    \$\begingroup\$ It is conceivable that Minecraft has patents on some of the things it does. If that is the case then you are violating those patents if you do them in the same way, even if you reverse engineer them. You also need to beware of the accusation that you are "passing your program off" as Minecraft, i.e. trying to make people think that your code is Minecraft, e.g. by making them look similar. \$\endgroup\$ – DJClayworth Jan 11 '12 at 17:39
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    \$\begingroup\$ You make a really good point, and I am not sure if Mojang has patented their game mechanics (if you can even do that?). Minecraft is such a mechanic driven game, that there isn't much to it besides the core concepts. I know that building and randomly seeded terrain generation aren't patented. I would beware of mentioning any relation to Minecraft and just develop something inspired by it instead of just reverse engineering it. \$\endgroup\$ – Brett Chalupa Jan 12 '12 at 2:51
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    \$\begingroup\$ Pedantic mode: using "Minecraft" in the name won't violate the copyright law, but it is very likely to infringe on the trademark, assuming they bothered to register it (which they almost certainly did). \$\endgroup\$ – RomanSt Jan 12 '12 at 18:48

Disclaimer: I'm not a lawyer. I'm answering this on best knowledge, might be wrong, though.

Yes, it's your work, you're allowed to do that. You can do with the stuff you write in your spare time whatever you want.

What you're not allowed is:

  • Use original source-code (decompiled) from Minecraft and put that under another license
  • Use original artwork from Minecraft
  • Use the name "Minecraft" as your own
  • Distribute the minecraft.jar

If you clone something, you need to watch out for possible copyright violations. Don't use anything which falls under Copyright. Copyright applies but is not limited to:

  • Sourcecode
  • Artwork (Graphics, Sound, etc.)
  • The name

So if you clone software (a game or an application), never use anything from that software directly, do it yourself.

  • \$\begingroup\$ Thanks for the answer. Two people telling the same, that sounds okay. I upvoted, but since the other answer came earlier I accepted that one. \$\endgroup\$ – Martijn Courteaux Jan 11 '12 at 16:17
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    \$\begingroup\$ The name is technically a trademark, not copyright. But in either case you can't use it, or anything that might be confused with it (probably like Mine-craft, though I am not a lawyer and that does not constitute legal advice). \$\endgroup\$ – DJClayworth Jan 11 '12 at 17:41
  • \$\begingroup\$ @DJClayworth: That's depending on the interpretation of the judge which rules over the case, I fear. There have been disputes in the past, f.e. Microsoft vs Lindows and Bethesda vs Mojang. \$\endgroup\$ – Bobby Jan 11 '12 at 21:03
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    \$\begingroup\$ I am not a lawyer, but duplicating a resource exactly by drawing every pixel from scratch is no different from copying the bits on disc, as far as copyright is concerned. \$\endgroup\$ – Blecki Jan 12 '12 at 4:28
  • \$\begingroup\$ @Blecki: Well, maybe clone was the wrong term. Of course you shouldn't redraw it pixel by pixel...but that's a rather blurry line. \$\endgroup\$ – Bobby Jan 12 '12 at 7:28

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