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Selling Games made with Blender & GPL/GNU Licensing

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Offline kat

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[image courtesy Blender.org]

Note: the following concerns issues of Licensing and Copyright and should not be construed as Legal Advice. If in doubt, do not assume, Consult appropriately qualified Council where necessary.

Q: I made a game with Blender Game Engine. Can I sell it?.
A: Yes you can.

Blender Foundation has made it explicitly clear that Blenders Game Engine (Blender Game Engine run-time) can be used to make and sell games and other projects commercially so long as relevant components are released under the same terms as the GPL/GNU License accompanying the application.

To understand this two points need to be made;
  • 1) anything MADE with Blender is considered OUTPUT and not related to the parent application [1].
  • 2) this being the case, licensing only then applies to the PARENT application and its derivatives [2].
In other words licensing requirements apply to Blender, Blender Game Engine (and distributable run-time) and their direct derivatives - re-brands, alternative builds of Blender itself, the Game Engine, would fall under GPL, NOT content subsequently made with those alternatives (subject to the following).

Understanding this is important because it directly affects the relationship game and content creators have with Blenders GPL/GNU and their material when wanting to distribute or sell BGE based games for commercial gain.

Blender Game Engine & Content Licensing
At face value then, the principle behind GPL/GNU Licensing might seem relatively straightforward; anything directly related to the application itself, or the Game Engine (and) run-time, is subject to GPL.

This is problematic however, because depending on the authors intentions, Blender Game Engine powered games typically require project materials to be 'packaged' into a self-contained executable, and in doing so then subjects everything contained to GPL/GNU exposure [3]. This is another core point to understand, that anything included in the run-time is exposed to GPL.

The way around this problem is to develop the project so the final game doesn't require media be packaged directly into the Blender Game Engine run-time [4]. This may be easier said than done but essentially the final games structure would be similar to the following;

Code: [Select]
 - bge.exe (2MB)
 - /assets/ (200MB)
 - - /models/
 - - /audio/
 - - /textures/
 - - /etc.

Instead of this;
Code: [Select]
 - bge.exe (202MB)

Link, don't Append
How this separation is actioned will depend largely on the game itself and the way its intended to work. Generally speaking however, where-ever possible "Link" rather than "Append" assets into a project - textures, models, audio should all be contained in external context-sensitive folders which ensures content is, and remains, outside Blender - at run-time generation only core scripts and files required to make the game function should be included, not the assets.

Selling games that use Blender Game Engine
With the above in mind then, the minuté of selling a Blender Game Engine product depends on whether or not the Author is willing to provide access to content 'flagged' as GPL/GNU, a decision that should be made at the projects inception because, as indicated above, doing so informs as to the structure and utilisation of the projects assets - self-contained run-time, or not as the case may be. With this done, should a customer purchase the game and make a request for GPL'd material(s), the Author only then need provide access to the actual component(s) explicitly subject to GPL/GNU etc. - either the entire packaged contents, or just the 'exe', again as the case may be.

In terms of how that relates to store fronts, distribution channels and the end product (selling on Steam for example), GPL'd content shouldn't have an affect unless third-parties have specific restrictions on the sale and/or distribution such material(s) [5]. Some do, so attention should be paid to their respective Terms of Service requirements beforehand (preferably at the planning stage) to make sure the eventual project can be sold via chosen outlets once completed [6].

[1] http://www.blender.org/support/faq/ - file OUTPUT, to third-party formats as well as *.blend, is not related to Blender from a licensing point of view because it's essentially considered to be nothing more than a databump (although proprietary in format, i.e. *.blend files can't yet be open in other applications because of the way they are formatted, not because of some restrictive interpretation of the license).

[2] GPL/GNU requirements apply to Blender itself and any derivatives of the application. For example if a new version of Blender were produced by a company absent core features, this new version would still be subject to the same GPL/GNU license requirements as the original 'parent' application which requires source data availability for each new iteration.

[3] any content packed into a BGE run-time is subject to the same license requirements as Blender/BGE because it's the executable package that's under license, not the content - include the latter into the former and its immediately subject to GPL.

[4] depending upon the version of Blender used, Game Engine projects are saved from the main "File" menu, usually as "File » Save Executable/Run Time" or from "Export" menu as "File » Export » Save As Game Engine Run-time", which may need to be activated as an "AddOn" from Blenders "User Preferences".

[5] the reason for this generally relates to Service Providers (store fronts) not wanting to get involved with the type of issues that typically accompany Copyright or Licensing GPL'd or otherwise 'open' software, and individuals selling content they may not actually have permission to do - it's something of a grey area where third-parties are concerned (reselling OpenSource Software) so distribution channels tends to stay away from it.

[6] although it's technically possible to split a game in two and sell the assets whilst giving the run-time away freely, it's unlikely Store Fronts will allow this because it essentially means they are potentially liable under various 'merchantable quality' laws for selling products that don't actually work (not fit for purpose).