I don't need to test my programs. I have an error-correcting modem.


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The Open Unreal Mod License (OUML) is a special Wikipedia:software license designed for open source and free game modifications for the Unreal Engine. It's meant to be a safe license to be used for your mod. The Wikipedia:GNU General Public License may not be safe to use for mods of the UnrealEngine. So that is the reason why this license has been set up.

The goal is to create a license analog to the GPL. the main addition would be that the mod is allowed to link to the (non-free) UnrealEngine as shipped by the publisher of the game using the UnrealEngine.

Key features:

  • the software is free as in speech
  • the original source must be available
  • code may be stripped from the package
  • the software may be linked with any UnrealEngine game (including art assests) whose EULA does not obstruct this license
  • software using this software must also be free software (analog to the GPL compatibility)

The license[edit]

You have to include a copy of this license with your mod.

       Open Unreal Mod License 
       Version 1.1, September 2005
       0. Definitions
       "Program"       the work, either in binary or source form, that has a notice 
                       attached to it stating that it has been released under this 
                       license by the copyright holder.
       "Modification"  a derivative of the Program or any other work based on the Program
       "Linking"       using parts of the Program, or using parts of any other work, 
                       thus creating a direct dependency between two Programs.
       "You"           the licensee
       "Runtime Environment"
                       the virtual machine or operating system required to run the 
                       Program, as released by the Publisher or Creator of said
                       runtime environment. This includes any extentions or updates
                       for the runtime environment released by the Publisher or 
       1. License
       Herewith everybody is granted permission to copy and distribute verbatim copies 
       of this document. The only restriction lies on changing the content, with the 
       exception to translation of this license.
       This license applies to the Program that has been released under this license. 
       The license only applies to copying, distribution and modification of the 
       Program. Execution or output of the Program are not covered by this license, 
       however the right for additional limitations on the use (that do not cover 
       copying, distribution or modification) is granted to the copyright holder.
       This license is only valid when all terms in this license comply with the 
       licenses of the dependecies of the Program. This includes the license of the
       possible required runtime envoirement.
       2. Copying and distribution
       You are granted to copy or distribute verbatim copies of the Program, on any 
       medium, or in any format as you see fit. You are not limited to charging a fee 
       for the physical act of transferring the copy, nor are you limited to provide 
       warranty for the Program in return of a fee. Unless this is prohibited by the
       license of the Runtime Environment.
       Any distribution of the program should be accompanied with a verbatim copy of 
       this license.
       3. Modification
       You are allowed to modify the Program, or portions of it, therefore making it a 
       derivate of the Program. You are allowed to distribute your Modification under 
       the following conditions:
               - You must clearly state that it is a modification of the Program
               - The original copyright notice must be kept intact
               - The modified files must contain notices of the changes made to it
               - The Modification must be released under the same license as the Program
               - Distribution happens in compliance with section 2
       4. Source
       The original source of the Program or Modification must be freely available on 
       5. Linking
       The Program or Modification may only link with other work that have been 
       released as free software.
       The license grants exclusive right to link with any non-free part of the 
       Runtime Environment, as provided by the publisher or creator of said Runtime 
       Using addapted portions of source code available in the runtime environment 
       in the Program is only allowed under the following terms:
               - the addapted code is clearly marked to originate from the runtime
                 environment, quoting the original copyright.
               - the following notice is added to the top of the file:
                 "This file contains portions of code from the runtime environment."
       6. NON WARRANTY

How to use[edit]

When you want to release your mod under this license you have to include the above license with your mod and add the following to every source file:

   <name of the program>
   Copyright (C) <year(s) of completion> <name of author>
   This program is free software; you can redistribute and/or modify 
   it under the terms of the Open Unreal Mod License version 1.1.

Important note

If you release your whole mod under this license it will also cover all other assets like maps, meshes, etc. If you do not want this you can dual license your mod (e.g. the code released under this license and the maps under an other "free" license). But be aware of the linking restrictions of this license.


When does linking create a direct dependency?[edit]

When you hard code references to an object or asset, it will be a direct dependency. Using DynamicLoadObject does not have to result in a direct dependency.

The question to be ansered is: will the program run without the dependency? If the answer is yes, it's not a direct dependency.

Other versions[edit]

Related pages[edit]


El Muerte: initial start, license needs to be filled in. Maybe we should also create a lesser OUML that would allow you to link to non free stuff (like art assets).

This is an initiative by the modding community. I doubt Epic will even officially support this license idea, but would be nice if they did. Oh and let's not make this a discussion about having your source available or not. Nobody is forcing you to use this to be license.

Tarquin: Interesting :) By coincidence, I was just pondering recently that we should have a standard license for the custom class scripts that are posted on the wiki :) Have you thought of looking into the Creative Commons licenses?

Sir_Brizz: Great idea...but the name seems...wrong? :)

El Muerte: since it's WIP, most things can change, so if you have a better name, let's hear it. Haven't read the creative Commons licenses yet.

El Muerte: well... any comments... (note: the lesser ouml would allow linking to non-free work)

pgibbs: Does "copyright holder" need defining explicity?

El Muerte: do you think it needs to be? Would be something like: "copyright holder" the person, group or company claiming copyright of the work

pgibbs: Perhaps: "copyright holder" the person, group or company claiming copyright of the Program.

El Muerte: it can't be the Program, because it obstructs with the definition of Program

Mr.Mitchell: Is "Envoirement" the correct word? It looks like "Environment" was intended, but since it has been written that way 3 times I am not so sure.

El Muerte: argh, yes it's "environment", for some reason I once had that confused and now it's sticking with me.

Tarquin: Is this ready yet?

luserSPAZ: Maybe this is obvious, but if you're going to propose this for widespread use, you should really have a lawyer review it first.

El Muerte: I think it's ready enough. Well it would be nice if a lawyer (or somebody else with more knowledge than me about this stuff) would look at this, but it's not a requirement. If somebody has some lawyer friends, let them take a look at this.

Foxpaw: I noticed one small issue in here - maybe it's a contradiction or maybe it just needs clarification. Part 2 suggests that you can copy or distribute by any means you see fit, so long as the work is not altered. It further goes on to suggest that you are not limited to charging a fee for the service of copying, etc. This suggests that you can retail the software to people, as the only mentions of charging for the software in section 2 explicitly state that you are not limited to charging for the service of distribution or warranty.

El Muerte: Uhm, yes. You could retail it (if you where allowed to by the license of the runtime). But keep in mind that everybody who get's a copy can distribute it.