OpenArena is released under the terms of GNU General Public License by Free Software Foundation.
This page tries to give some help about which stuff can be imported/exported into/from OpenArena from/to other "free software" projects/repositories.
OpenArena uses the same "copyleft" license for both source code (which is based upon Q3A GPL source code release, plus years of fixes and additions) and assets (which have been either redone from scratch, or imported from other GPLv2-compatible sources, such as Public Domain/CC-0 licensed stuff).
It is possible to re-use OpenArena stuff under the terms of either Version 2 of the license or (at your opinion) any later version. With the "any later version" thing, the license is also colloquially known "GPLv2+", and it means that you are allowed to re-use its code/assets in both GPLv2 and GPLv3 projects. But not the other way around: GPLv3 stuff cannot be imported into OpenArena.
You can find a copy of the license text in COPYING file. Here's a link to an online version by Free Software Foundation: https://www.gnu.org/licenses/old-licenses/gpl-2.0.en.html.
Important: please notice that while "official releases" by OpenArena Team follow that license, additional assets by the OpenArena Community or by third party in general (e.g. maps, mods...) may follow different licensing. This is one of the reasons automatic downloading is disabled by default.
Into the GPLv2 license
In short, the license is comprised of four freedoms:
- Freedom to use
- Freedom to distribute
- Freedom to derive from it
- Freedom to distribute the derivations
In order for all of these freedoms to be achieved, the asset must include a license file and the source used to create the asset:
- In general, assets released under the Public Domain and CC0 licenses are in by default. Then again, make sure to check!
- Texture sources include Gimp's .xcf and Photoshop's .psd files.
- Model sources include Blender's .blend files.
- Sound sources include Audacity's .aup files.
We shouldn't have to clarify this, but it's necessary: COPYRIGHT INFRINGEMENT IS A NO-NO. That is followed by lawsuits and Cease-and-Desist letters. We don't want to deal with that.
Why GPL?
- For easiness of maintenance: Having the source at hand allows us to fix whatever is wrong with the assets without the need of the original author being around.
- For a wider inclusion: GPL automatically respects Debian's DFSG, which allows OA to be distributed with many distros. It also allows OA to be distributed in commercial distros, even though people developing OA receive the exact amount of $0 for its development.
Some reminders
- A reminder for mappers and content creators in general: there are various games out there which "are GPL'd", but often that only refers to source code (engine and/or gamecode) and NOT to their assets. A classic case is Q3A: its textures, models, shaders are still copyrighted. Also, "freeware" software does not mean "free software" as in copyleft/opensource. Just to say to double check the license of the third-party content you may be planning to reuse in your maps.
- You can see "GPLv2+" mentioned somewhere. That "+" is a colloquial way to refer to a gpl license text which includes a phrase about the fact that the stuff can be reused under the terms of GPL, "either version 2 of the License or (at your opinion) any later version."
This means that third party people can reuse gplv2+ stuff and import them into their gplv3+ projects if they wish. NOT the opposite (we cannot import gplv3/gplv3+ stuff into OA).
If you look into OA "copying" file, you find that phrase in there... so OA license is GPLv2+ and thus, for importing stuff into oa, "gplv2 only" (without that phrase) is not really okay. Check the license files to search for that "any later version" phrase. - The code of many old mods and old coding "tutorials" designed for Q3A was founded upon the Q3A SDK and not the Q3A GPL release. Such stuff is not GPL-compatible, so you are not legally allowed to mix such code with GPL code. Many old mods do not mention any licensing infos, but it's probable they fall under the Q3A SDK EULA. Such EULA probably states that stuff has to be used with Q3A, hence even just using such mods (but probably even just maps or models) with OA is at one's own risk.
Releasing GPL-compliant stuff
- If you wish to release a GPL-compliant map, please refer to Mapping manual/Appendix F: GPL Compliance and Mapping manual/Compiling and packaging.
- If you wish to release a GPL-compliant player model/bot.... [TODO]
- If you wish to release a GPL-compliant mod.... [TODO]
External links
- GPLv2 on Gnu.org
- GPL Frequently Asked Questions
- Compatibility table of the various GPL licenses.
- GPLv3 Quick Guide, which explains that GPlv2 with the "any later version" phrase can be imported into GPLv3 projects (but not the other way). Also shows a graph about some licenses which can be used to import into GPLv2 projects.
- Wikipedia article about GPL