[Bf-committers] extension clause

David Jeske davidj at gmail.com
Mon Nov 15 21:39:23 CET 2010

I apologize in advance for the long post.

(1) @ Ton : this is not a perception issue, this is the current legal
interpretion of the GPL. It is not legally okay to write, use, or distribute
binary code modules that links directly with, and is dependent on, GPL code
without triggering a need to GPL that code. In addition, doing so implicitly
licenses all applicable patents to the community. In short, it's not legal
to write a closed-source extension for a GPLed package such as GIMP or
Blender. I believe this will hurt Blender's long-term prospects for
adoption. I don't know what solutions are possible (if any), but I think
it's important to figure out. Carving out an LGPL extension API (something
that would not require relicensing of existing code) might fix this.

This Blender "faq" is naively incorrect and should be fixed...

*Can my organization use Blender internally without giving up our valuable
changes to our competitors? The GNU GPL does allow your organization to use
a modified version of Blender internally without offering the source-code as
long as you do not distribute it outside your company or organization.*
There are many problems with this interpretation, both legally and
practically. I'd like to stay out of a huge legal debate about the GPL, so
I'll just point out the practical problems. The practical realities of
"distribute" and "organization" are too constraining.  Companies today work
with contractors, third parties, outsourcers, etc, which are technically not
part of the "organization" but which help produce the work. People are not
puppets, and companies do not have enough control to assure that nothing is
ever "distributed", thus triggering the need to GPL and open-source. Which
causes companies to refuse to accept any GPL code into their source-control
or development pipeline.

These and many other factors mean this should read:

*Can my organization use Blender internally without giving up our valuable
changes to our competitors? 3d models and data produced by blender can be
output in a variety of formats and may be kept under any license the author
chooses. Changes to blender source code are governed by the GPL and must be
distributed as required by that license. *

This gets blender out of the situation of being wrong about interpretion of
the GPL, as it simply defers to the GPL.

(2) As Lorenzo excellently explained. This is not a discussion about
allowing commercial companies to use blender code in their own products.
This is a discussion about allowing commercial companies to use Blender,
become part of the community, and contribute.  John Grant very eloquently
explained the issue in the form of his specific example. I'd like to quote
his words here to reinforce them..

*"Because there is no protection for companies that want to extend Blender,
I can not recommend we use Blender in our work processes.  Since we can not
develop tools that integrate with Blender, we have been forced to integrate
with Autodesk tools.  Our clients are familiar with the Autodesk tools and
are happy about our choice.  The Blender community has lost a chance to
introduce itself to our clients."*
As an interesting datapoint. GIMP is under the GPL, and has these same
limiting issues (no commercial extensions), and yet companies are "selling"
gimp for their own profit, because nothing about the GPL disallows this.
They simply package and sell it, source included. Being under the GPL does
not prevent this.

(4) Linux is not entirely built of GPL code as it would lock out commercial
involvement. They smartly use LGPL and draw boundaries so the community can
still build a healthy ecosystem of open-and-closed source tools around
it. In fact, using Blender on Linux is in part practical because xfree86 is
not under the GPL, facilitating binary 3d drivers from NVidia to be used on

A 3d tool like blender is not like gcc. It is not an isolated tool that
exists without in-address-space extensions. In order to make good use of 3d
tools in a pipline, software is frequently built and intergrated with it as

(5) Several folks here have brought up the point that it may be difficult
(or impossible) to do anything to alter Blender licensing, even if there is
a good alteration that could be made. I understand this point, and will
offer that it will only get harder as time goes on. I revived this
discussion because I'd really like to see Blender become a tool on-par with
Maya, 3dsmax, and others. I don't believe this will happen unless commercial
companies can use proprietary code in extensions without legal fear of the
GPL -- because that positive feedback cycle will bring more professional
users and developers to Blender.

(6) To followup on Lorenzo's excellent suggestion for specific examples...

Pixar authors the Renderman rendering engine. They also have their own
modeling/animation tool called Marionette. They use Maya and Max as well. It
would be very scary for them to link renderman into Blender, because of
potential GPL issues. They might have animators that use Blender to kick out
a model or edit verticies, but it would be legally scarry to integrate it.

Electronic Arts primarily uses Maya for modeling and animation. They
use proprietary and 3rd party tools for handling components, such as
compressed-textures, compressed-animated-meshes, and physics. These
components are integrated into their 3d tools environment, and also licensed
commercially for inclusion into their distributed games. It is legally
dangerous to integrate components like this into Blender for their own use,
because of the strictness of the GPL. Again, this is the reason libc is
under the LGPL instead. It assures the freedom of libc without trying to
contaminate all other code that links with it.

In game companies in general, it is common to integrate game-engine
renderers into the 3d modeling environment, so artists can see assets
rendered as they will in the game engine. This is legally dangerous if the
3d tool is under the GPL and the game engine is closed source.

- studios:
> studios are (usually) only interested in spitting out frames at the highest
> quality and in the most efficient possible way. They develop an incredible
> amount of software internally, but are not interested in selling it outside
> because it would take too much hassle to polish it enough for selling...
> it's more profitable for them to work on the next movie! But sometimes they
> do distribute it outside, and when they do is almost always as open source:
> http://opensource.image-engine.com/
> http://opensource.imageworks.com/
> http://www.disneyanimation.com/technology/opensource.html

These examples reinforce my point. They are tools written around commercial
packages. What they are doing is similar to writing photoshop plugins (i.e.
plugins for existing commercial software). There is no concern that the
licenses for these commercial packages can force them to release their code
before they decide to open-source it. Of course when that time comes, they
are free to do so. This is a demonstration of the positive cycle of
community contribution that can come when companies develop around a tool
(such as Maya, Houdini, etc.)

This is similar to the GIMP plug-in issue. Many interpret the GPL to mean
that GIMP plug-ins must be GPL as well. (i.e. they are not independent and
seperate, because they depend on the GIMP plug-in API) GIMP tries to support
commercial Photoshop plugins to get access to the functionality. It doesn't
work well and will keep GIMP always in Photoshop's shadow. There are many
reasons these companies don't provide plugins for GIMP, I believe one of
them is GPL contamination licensing issues.


Separate these key points and consider for yourself...

(a) will Blender benefit from having more users / developers, in particular
those professionals at VFX and gaming companies?
(b) will Blender benefit from having VFX and gaming companies be able to
standardize on and build around Blender?

If your answer to these these points is "no", while I can see your
perspective, it's not one I share. If your answer to these questions is
"yes", then recognize that the current straight GPL license is a roadblock
to these things happening. Can we come up with creative solutions?

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