Important Question Regarding ADDONS & GPL

[JulianSeverin (Julian Eisel)]

@LazyDodo

That would fix the linking issue, but that would still leave the distribution issue, afaik you cannot ship this .exe in the same package with your gpl code?

There is a bit of a grey area involved here, but reading skw’s suggestion, I don’t see a GPL violation in there. Only when the .exe and the GPL’ed code were “designed to run linked together in a shared address space”.
It’s explained pretty clearly in the GPL2 FAQ.

[TIAN-SKY.com]

@skw

Function calls from C or Python require that you link against the library providing the implementation. This is definitely linking as defined by the GPL. For example, calling the C function time() from time.h means that you’re linking.

On the other hand, calling the command line tool “date” from your code and parsing its string output is not considered linking.

In the context of Blender, if you have a .dll/.so/.dylib that provides a certain function (say, a boolean of two meshes), using that .dll from a Blender add-on requires that the add-on and with it, the dll must be distributed under the terms of the GPL. It doesn’t matter if the .dll is renamed to .pyd, is called via ctypes, wrapped in SWIG, etc - it’s considered linking. Now, turn that .dll into an .exe that takes two OBJ files as input and returns a new OBJ as result and call that from your add-on, the add-on must still be under the GPL but the .exe is not required to.

As a rule of thumb: if your code doesn’t show up separately in the Task Manager (ps on Linux), it’s linked to Blender. If it shows up separately in the Task Manager, you’re not linking.

Yes, this is what I meant to say. I used the term “function call” to mean what you said. I don’t tend to over-complicate programming terminology, as I like to keep it simple and effective.

[Fweeb (Jason van Gumster)]

@TIAN-SKY.com

Yes, this is what I meant to say. I used the term “function call” to mean what you said. I don’t tend to over-complicate programming terminology, as I like to keep it simple and effective.

Except no. Some words have very specific meanings (especially in programming). By conflating and overloading terms, you’re not keeping things simple and effective. You’re complicating them by being unclear.

[TIAN-SKY.com]

@Fweeb

Except no. Some words have very specific meanings (especially in programming). By conflating and overloading terms, you’re not keeping things simple and effective. You’re complicating them by being unclear.

My bad, as I am a person who prefers Assembly and programming class inheritance using C over C++.

But anyways, we seem to have come to a consensus and answer to the often asked question of using non-GPL binaries with GPL software. If the non-GPL code does not contain GPL code, and both programs merely talk by passing data, then it is permitted. Any objections???

I know this not only affects me, but many people and corporations are hesitant because of these concerns. So by clarifying this we can come to better understanding of GPL. If Richard M Stallman can give us his official opinion, that would help.

[skw (Stefan Werner)]

@TIAN-SKY.com

But anyways, we seem to have come to a consensus and answer to the often asked question of using non-GPL binaries with GPL software.

The consensus is: Don’t.

If the non-GPL code does not contain GPL code, and both programs merely talk by passing data, then it is permitted. Any objections???

Yes. See the GPL FAQ:
"If the main program uses fork and exec to invoke plug-ins, and they establish intimate communication by sharing complex data structures, or shipping complex data structures back and forth, that can make them one single combined program.

If Richard M Stallman can give us his official opinion, that would help.

It’s all spelled out in the GPL FAQ. That is the official opinion.

[TIAN-SKY.com]

@skw

The consensus is: Don’t.

Yes. See the GPL FAQ:
"If the main program uses fork and exec to invoke plug-ins, and they establish intimate communication by sharing complex data structures, or shipping complex data structures back and forth, that can make them one single combined program.

It’s all spelled out in the GPL FAQ. That is the official opinion.

Thanks. So we just need to avoid using ‘fork’ and ‘exec’, and communicating using ‘complex data structures’.

Let’s see how this goes…

[skw (Stefan Werner)]

I strongly suggest you read the GPL FAQ: https://www.gnu.org/licenses/gpl-faq.html#GPLPlugins
It is not at all defined by whether you use or don’t use fork/exec, it’s about how intertwined the two programs are.

If the main program uses fork and exec to invoke plug-ins, and they establish intimate communication by sharing complex data structures, or shipping complex data structures back and forth, that can make them one single combined program. A main program that uses simple fork and exec to invoke plug-ins and does not establish intimate communication between them results in the plug-ins being a separate program.

(emphasis mine)

If you need a definitive answer, ask a lawyer and not a web forum. For all you know, I could be just some random drunk guy with internet access.