[Bf-committers] extension clause

David Jeske davidj at gmail.com
Mon Nov 22 20:51:30 CET 2010

On Mon, Nov 22, 2010 at 10:40 AM, Dan Eicher <dan at trollwerks.org> wrote:

> > How is legally viable to make a capable BSD licensed API with the code
> under
> > the GPL? The shim would be dependent on material details of the Blender
> > design and internals. It would probably expose many of those details
> (such
> > as UI panels, RNA) As a result, the shim should be under the GPL, and as
> a
> > result, the extensions should be under the GPL.
> The same way the (BSD licensed) ofx api can load proprietary code/libs.

BSD Licensed code can do anything it likes. BSD license does not attempt to
control the license of other code it links to like the GPL does. This is not
a valid example.

> Blender can link to the header files and the *users* load/link to the
> non-gpl compatible external code (which also links to the BSD'd header
> files)... everyone gets what they want and no copyrights are violated.
> Drinks for everyone!!!

Although the BSD above is confusing the example, I agree that by my read of
the GPL, an open-source GPL blender extension can load/call to a third-party
closed-source binary code library under the GPL's "library exception". What
this means is that any extension UI, code that touches RNA, any code which
touches any detail of blender would need to be open-sourced under the GPL.
While the "core algorithm" which must not be at all dependent on or link
against blender details, can be closed-source.

This is unlike extensions for tools such as Maya or 3dsmax, where the entire
extension, including UI and data-manipulation may all be closed source. I
believe this means some types of commercial extensions are viable (such as a
file format reader/writer), and some types of commercial extensions not as
viable (a UI extension or addin based on data-transformation within
blender). I'm undecided whether this is enough. A company considering
releasing an extension for blender may find the idea of having to
open-source a chunk of the extension is unfamiliar, which might prevent them
from doing it. However, it looks like that chunk would merely contain
glue-code that doesn't reveal their proprietary invention. I'll need to
think about this some more and consult some contacts in the industry to form
an opinion. This is an excellent point (which I think has been mentioned
before, but I didn't quite see it this way until your paragraph above).

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