Licensing is not the most exciting topic, but if you wish to contribute, you will absolutely need to read it.
Since SuperTuxKart is included in many linux distributions with strict license requirements (e.g. Debian), we cannot accept tracks/karts/textures/etc. with unclear licensing terms. Furthermore, we are hosted (freely, I might add) by SourceForge, which requires that all hosted materials be released under open licenses; therefore posting materials with improper licenses would violate our terms of hosting
The source code of SuperTuxKart is released under GPL v3.0 (we updated all files to use this version by making use of the "or (at your option) any later version" clause of the GPL).
Considerations to always keep in mind
If you wish that your contribution be included in STK main or add-ons, always note down the author's name, website where image was found and full license name of everything you use (textures, models, sounds, etc.); when you make something yourself also note that you did it yourself and which license you release it under; we recommend making a file named "License.txt" to contain all this information; if we do not receive this information along your track/kart/etc., we will be legally unable to use your contribution in any way!
If you reuse a texture from another STK track, ideally still note down its author and license, by reading the appropriate License.txt file, a simple reference to another track makes things very hard to follow (rationale : the other track might get removed, or the original texture may be replaced with another texture of a different license or by another author, and then all links between tracks from license files become broken).
Also be sure that you have the right to actually release the art work under the license you chose. Some (typically commercial) software might restrict what you are allowed to do with anything created with that software.
Brands, corporations etc
Trademarked logo and brands aren't allowed in SuperTuxKart. Instead if you want to add a company or a corporation you can use fictional ones from our universe.
Our license of choice is Creative-Commons-By-SA version 4.0 or more recent (Note: Creative Commons is hereafter abbreviated CC). Version 3.0 of the CC licenses is also OK but lacks the more uniform international application of version 4.0.
- Note that "I asked the guy and he said 'yeah you can use it'" is not a valid license (yup, happened). (If you ask someone to release their work for use in STK, please request an explicit statement that the work be released under CC-BY-SA 3.0, or GPL, or another free license)
- Also note that even if you modify the work (image, model, ...), in general you do not have the legal right to change the license of your modified version; changing of license must be explicitly granted by the license of the work in question, or by the author.
These licenses are acceptable : CC-BY 3.0, CC-BY-SA 3.0, CC-BY 4.0, CC-BY-SA 4.0, GPL, LGPL, Apache License, Mozilla License, Artistic, MIT, BSD License, X11 license, CC0 (Public Domain)
Licenses that can be used as a base for derivative works : CC-BY 2.0 / 2.5, CC-BY-SA 2.0 / 2.5. If you find an image released under this license, it is NOT acceptable to use this image directly in your work, however you are allowed to make a significant modification to it (for instance crop it and make it repeatable to build a texture) then you are allowed to release your modified version of the image under the same license, version 3.0, which is accepted. What constitutes a significant modification is open for lawyers to debate upon but as long as your modified version does not look like a copy of the original we won't be picky.
These licenses are NOT acceptable : GNU Free Documentation License, Creative Commons Sampling Plus, any Creative Commons with the "Non-Commercial" clause, any Creative Commons with the "No Derivatives" clause, Free Art License, CGTextures License, Image*After Terms, Mayang license, TextureArchive Terms, "Creative Commons" alone without a version number or without full name
For other licenses, we need to check on a case-by-case basis
"GPL" or "CC-BY-SA" is not specific enough. Please, specify a specific version(s) of the license like "GPL 2+" or "CC-BY-SA 4.0". There are significant and incompatible differences between versions of some licenses.
There is yet another thing to consider :
- Not all licenses are compatible which each other. This means you need to be extra careful when combining works that are under different licenses.
- For instance, I (User:Auria) have no idea if CC-BY-SA 3.0 and GPL are compatible. This means that if you make a texture by combining elements from a CC-BY-SA 3.0 texture and elements from another GPL texture, we will be in unknown territory until someone can give us legal advice whether this is possible or not.
Where to find files
Looking for properly licensed material?
The following websites offer only public domain material, that is always OK to use :
- Public Domain Pictures (Photo)
- BurningWell (Photos)
- PD Photo (Photos)
- pdsounds (Audio)
- OpenClipArt (2D Vector Art)
The following websites provide resources under a variety of mixed licenses; you may find a lot of good material there but verify the license on a case by case basis :
- OpenGameArt (Textures, 2D art, 3D models, audio)
- swtexture (Textures)
- Freesound (Audio)
-  (Textures)
- wikimedia commons (Photos, drawings, audio)
- ccmixter (Audio)
- sound bible (Audio)
- Community Audio (Audio)
- Jamendo (Music)
- BlendSwap (3D models)
- Blender Model repository (3D models)
-  (a full list of sites with Textures, 2D art, 3D models, audio)