On licensing Blender forks

On the License subject, Cycles is Apache License, not GPL. K-Cycles and E-Cycles authors only have to share code changes made in Blender.

Hi, this has been discussed before in developers thread. This is about distribution of combined licenses:

The important point is when they are distributed in a combined work (the definition of “combined work” is a discussion on its own), that has to be done in a GPLv2+ compliant manner. Since parts of Blender are not license compatible with GPLv2 (e.g. Cycles’ Apache 2), but only GPLv3, any combination of Blender with these parts has to be distributed under GPLv3.

And this about MODs obligations regarding code publication/distribution:


In this post: E-Cycles - Fast Professional Rendering, 100% compatible with Cycles! NEW: 2.93.1 available! - #4001 by bliblubli, @bliblubli said that E-Cycles is GPL. It’s sad that he doesn’t fully respect it. I hope @eklein won’t do the same.

To be honest, I am a bit surprised that @bartv and @moderators allow add-ons developers not to respect software licenses on the forum.

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Blender Artists is an independent Blender community platform. We do not act as license police, so to speak. We do keep an eye on discussions, also about this subject. If the discussion derails into a heated debate, we will step in.


I am not a lawyer. So I can’t say what is the exact GPL distribution responsibility for a Cycles modification. I do know that OTOY corporation with lawyers in their staff. Their custom build of Blender with Octane is not deliver with source code. Maybe this GPL discussion of custom builds could be move to a separate thread.

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Agreed, done.


What is the Cycles licence finally? Would it be theoretically possible, for example, to place a commercial version of Cycles in the App Store (as a Blender addon) - without having to publish the code?

For reference, all information about Blender licensing is available here:

From what I read here, you’re free to sell Blender add-ons and forks, as long as they respect the GPL, meaning you need to provide the source code to buyers.

It seems E/K-Cycles and any other developers can release and sell their own Cycles versions without the source code publishing:
Blender Cycles rendering engine is available as [Apache 2.0](http://opensource.org/licenses/Apache-2.0).

Rhino uses Cycles and there are no source code available. The same with Octane.
E/K-Cycles developers (and other) should consult a lawyer and explain the situation because it looks like they are not fully prepared to run a business. That is amateurish at the moment.

If it is known that an addon/fork is license incompliant, would you still allow their threads on your forum? Would you allow their ads to run on your site?

I am trying to understand what not being a license police exactly means.

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That’s the Apache side of the story, there is also the GPL side. You might want to check this out.

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Is Octane Blender source code available somewhere?
Is it illegal for OTOY to release its own version of Blender?

Whether GPL applies or not depends on how your non-GPL code is integrated. If, for example, a renderer is running on its own process and the addon (or fork) is communicating this via IPC, GPL does not apply.

Cycles is integrated into Blender and AFAIK it doesn’t run as a separate server, so GPL applies when bundled.


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It means that Blender Artists is a free, independent platform for Blender users, Blender developers and other Blender enthusiasts. We moderators spend daily free time on keeping Blender Artists a nice place, but we don’t have the time to verify if every add-on that is posted here is correctly compliant with the involved licenses.

:point_right: Edit: I wrote this with add-ons in mind, such as E-Cycles, because this thread sprung from that discussion, but a whole Blender fork is another discussion.

Thank you for your response. You don’t have to answer my 2 questions. But if you did answer, that would be nice. Let me write them down again for your convenience:

If it is known that an addon/fork is license incompliant;

  • Would you still allow their threads on your forum?
  • Would you allow their ads to run on your site?

If it is fully clear that someone is breaching a license or copyright, we may decide to act accordingly, although we are not an official Blender site. But for example the E-Cycles case is an unclear case that has sparked a lot of discussion between proponents and opponents, so we are closely watching the thread’s development.

This is something you’d have to ask the BA owner, @bartv . I’m just a volunteer.

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Got it. So it seems you don’t have a policy in place (otherwise you would’ve known I guess). Thanks.

As far as I know there is no general Blender Artists forum policy regarding add-on licensing matters, we look at each individual case and if necessary we discuss it among the moderators.

If it is clear that someone is violating the license then no, we would not continue to promote them in any way. As this is a complex topic though, we can’t rely on ‘opinions’ and we’d need to see a statement by some authority like the Blender Foundation first before making such a decision.


To be honest my previous replies were written with E-Cycles in mind, and then I realized this is a split-off thread that has gone in a broader direction. :blush: