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Questions about GPL license

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Questions about GPL license

Postby NewFlyer153 » Wed May 29, 2019 9:49 pm

Hi, I'm new to this board. I've read some information about this great project, but I'm unsure about some things regarding the GPL license. I understand the GPL allows a person to do almost anything with the software (limited restrictions), however the condition is that in many cases the new software you make which includes GPL software must be made open source, or at least available to anyone who requests the source. I understand this is what Flight Pro Sim has done. They have made their product a commercial one, but must provide the source for anyone who requests it.

My question is a little less simple than the above case, because the GPL as I understand was mainly written (if I understand correctly) to affect software, ie., code, programming. My question is about the 3D models, which are also licensed under GPL.

If for example I make a game and I include an aircraft from FlightGear in it, it doesn't make much sense to talk about making the source code available because what I've used in it is just the 3D models and textures. Unless it is required that the source code of my entire game must be made open source. I am wondering if this is required.

Likewise, if I have my own 3D model of a plane in my game, and I wish to use the cockpit models and textures from a FlightGear aircraft, what is it exactly that I need to make publicly available. I am happy to make available any models and any changes I make to it (for example a cockpit or a plane), but by doing this, does it mean that I need to make publicly available the entire plane? Or the entire game open source?

As another concrete example, there is a popular contributor here with the username Helijah, who has his own hangar, who has made his aircraft available for download on Sketchfab under a CC BY (attribution) license. If I were to use this aircraft in my game, I would have to attribute Helijah. No problem there. But say I used a cockpit from another of the aircraft here (which are licensed under GPL as far as I know), does that mean my game has to be open source? Or that any plane I use the cockpit in has to be made publicly available?

Thanks in advance for any information about this. Licenses can get pretty complicated.
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Re: Questions about GPL license

Postby Thorsten » Thu May 30, 2019 5:20 am

If for example I make a game and I include an aircraft from FlightGear in it, it doesn't make much sense to talk about making the source code available because what I've used in it is just the 3D models and textures. Unless it is required that the source code of my entire game must be made open source. I am wondering if this is required.


Basically yes [1] - if you include GPL licensed content in your software, you need to license all your software GPL as well and make the source code of all of it public. That is by design - GPL is a license that is intended to make OpenSource content widespread and does not allow you to selectively apply it.

The case is different with pure attribution licenses, these you can include in a commercial project.

What you can always do though is to contact the original author(s) and ask to dual-license their work.


[1] The legal grey area here is bundling - if it is clear in form (aka written on your download page) and function (the part works without the other) that you have e.g. a software and an independent addon, that addon could potentially be of a different license (note that it is impossible to give definite advice here, a court would ultimately have to settle such a case).

One could e.g. plausibly argue that any given airplane is an addition to FG (and there could be aircraft addons under a commercial license if there were a market for them) but one can likely not plausibly argue that a cockpit 3d model is an addon to an airplane.
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Re: Questions about GPL license

Postby NewFlyer153 » Thu May 30, 2019 6:18 am

Thank you, Thorstein. I suspected that anything GPL incorporated into your project would require you to make your entire project GPL. I think technically this isn't true 100% of the time. For example, there are cases where using a GPL library in your code won't require you to make your entire code GPL. I've read differing accounts about whether linking to a GPL library requires this or not.
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Re: Questions about GPL license

Postby Thorsten » Thu May 30, 2019 6:46 am

For example, there are cases where using a GPL library in your code won't require you to make your entire code GPL.


No, that's specifically covered by the license - using a GPL lib for sure means your entire code has to be GPL - that's the original purpose and intention of the GPL (what you've read about is probably the LGPL license).

I've read differing accounts about whether linking to a GPL library requires this or not.


It's the internet and you can read any opinion about anything, but there's no legal webpage which will tell you you can get away linking to a GPL lib without licensing GPL. It's a very simple case and it's plain illegal 100% of the time.
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Re: Questions about GPL license

Postby Icecode GL » Thu May 30, 2019 8:25 am

Quick note: what Thorsten said applies if you are going to distribute your software. If you don't plan on distributing it, you can do anything you want with GPL-licensed content.
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Re: Questions about GPL license

Postby bugman » Thu May 30, 2019 8:33 am

The only way a GPL-licensed library (rather than LGLP-licensed) can be used in non-GPL-licensed code is if the library is dual licensed. As for applying the licence to content that is not computer code, see the GPLv3 licence text for a legal clarification:

The “source code” for a work means the preferred form of the work for making modifications to it.


I.e. this licence can literally be applied to anything protected by world-wide copyright law.

Regards,
Edward
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Re: Questions about GPL license

Postby bugman » Thu May 30, 2019 9:00 am

Including GPL-licensed cockpit components into another "whole" aircraft could be argued in 3 ways:


Regards,
Edward
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Re: Questions about GPL license

Postby Thorsten » Thu May 30, 2019 12:05 pm

Quick note: what Thorsten said applies if you are going to distribute your software. If you don't plan on distributing it, you can do anything you want with GPL-licensed content.


Yes, quite true.
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Re: Questions about GPL license

Postby NewFlyer153 » Thu May 30, 2019 4:28 pm

Thorsten wrote in Thu May 30, 2019 6:46 am:what you've read about is probably the LGPL license.


Yes, that's most likely what I'm thinking of. Thank you clearing up some finer points. Still, I find the whole situation a bit strange. I gave the example of people being able to do nearly whatever they want with it, and I gave the example of what Pro Flight Sim have done, and unlikely others have done the same thing. The condition to selling this same product for commercial profit is that they make the entire source code available to anyone who requests it.

However take a slightly different example. I can take the 3d model of a plane in one of the repositories, convert it to obj. or fbx. or blender format, (or anything else), sell it, make a profit, and no additional conditions would attach to that (ie., providing anything extra such as source code, because there is no source code). Is that correct?

Also another point I want to clarify. The great artist Helijah has made many (probably most) of his aircraft available for download under the CC-BY (attribution) license on Sketchfab. CC-BY (I'm not sure) allows the sale of the product, it's just that attribution has to be made. As far as I know these same aircraft are available for download here, but are probably licensed under GPL, keeping in line with FlightGear's license itself. If that's true I can take the model and sell it for a profit (without crediting Helijah), and I can do so without any other conditions, because the model stands by itself, (that is, there is no source code to speak of, it's a 3D model). Have I basically got this right? If so, it seems rather strange.
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Re: Questions about GPL license

Postby Thorsten » Thu May 30, 2019 4:49 pm

The condition to selling this same product for commercial profit is that they make the entire source code available to anyone who requests it.


Free software means 'free' as in 'everyone can take a look into the source code, modify it and re-distribute it', not as in 'no cost'. So basically yes - you can create a product and make a profit from it, but whatever you change and add has to be available for others in source and under GPL license.

I can take the 3d model of a plane in one of the repositories, convert it to obj. or fbx. or blender format, (or anything else), sell it, make a profit, and no additional conditions would attach to that (ie., providing anything extra such as source code, because there is no source code). Is that correct?


No - Edward gave a definition of what 'the source' is in case of 3d models - this is what you have to make available.

CC-BY (I'm not sure) allows the sale of the product, it's just that attribution has to be made. As far as I know these same aircraft are available for download here, but are probably licensed under GPL, keeping in line with FlightGear's license itself. If that's true I can take the model and sell it for a profit (without crediting Helijah), and I can do so without any other conditions, because the model stands by itself, (that is, there is no source code to speak of, it's a 3D model).


It's a dual-licensed model - you can take the CC-BY version and adhere to the CC-BY license, or you can take the GPL version and adhere to the GPL license. You'll find that the GPL license does not work 'without any other conditions' once you read it and that CC-BY is much more permissive.

If so, it seems rather strange.


It is not if your aim is to have everything modifiable and re-usable by everyone else.
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Re: Questions about GPL license

Postby NewFlyer153 » Thu May 30, 2019 5:34 pm

Thorsten wrote in Thu May 30, 2019 4:49 pm:
I can take the 3d model of a plane in one of the repositories, convert it to obj. or fbx. or blender format, (or anything else), sell it, make a profit, and no additional conditions would attach to that (ie., providing anything extra such as source code, because there is no source code). Is that correct?


No - Edward gave a definition of what 'the source' is in case of 3d models - this is what you have to make available.



I'm sorry I don't know who Edward is. The point I was making about additional conditions is that the "source" of a model licensed under GPL and sold is everything that you sell or distribute. I take GPL-licensed model and sell/distribute it, that's all the "source" that I need to provide, to the person I distributed it to. Right?

Thorsten wrote in Thu May 30, 2019 4:49 pm:You'll find that the GPL license does not work 'without any other conditions' once you read it and that CC-BY is much more permissive.


I know the GPL license has conditions, but what I am saying is that in the case of the 3D model example the conditions have already been fulfilled by the mere distribution of the 3D model, because that is the "source".

I thank you again, Thorstein, for all your help. I know I should be asking this at another place, but seeing as you're rather knowledgeable about this copyright stuff I thought I might ask you. GPL and CC Sharealike have been described (pejoratively or not) as licenses that "infect" anything that it is used with. In the case of CC Sharealike my understanding is that using a CC-SA product with your own private product may constitutes a derivative work. If this is the case, does this mean that your ENTIRE work must be shared? I'll give you an example.

Wikipedia:

"approved the adoption of the Creative Commons Attribution-ShareAlike (CC BY-SA) license as the main content license for Wikipedia and other Wikimedia sites."


If I make a film and use a photo from Wikipedia that is licensed under this CC BY-SA license, does my film become a derivative work and therefore must be licensed under CC BY-SA also? The same question goes for any other artwork or computer renders.

It would make more intuitive sense to me that you would be required to share the photo and any changes you made to it, instead of licensing the entire product or artwork you used the photo in under the same license.

I'm wondering, in the case that a photo or 3D model is licensed under GPL, you have already said that the entire product that uses the GPL content must be licensed under the same license, not just the specific content (ie., photo, movie, 3D model). Would this go also for the sharealike component of CC BY-SA? That is, if I use CC BY-SA content in a work, a video game, film, collage, slide presentation etc., the entire product must be licensed under CC BY-SA as well?
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Re: Questions about GPL license

Postby wkitty42 » Thu May 30, 2019 11:57 pm

NewFlyer153 wrote in Thu May 30, 2019 5:34 pm:I'm sorry I don't know who Edward is.

that's bugman and he always signs his posts with his real name ;)
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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Re: Questions about GPL license

Postby Thorsten » Fri May 31, 2019 4:47 am

I'm sorry I don't know who Edward is.


The person signing his posts with Regards, Edward...

I know the GPL license has conditions, but what I am saying is that in the case of the 3D model example the conditions have already been fulfilled by the mere distribution of the 3D model, because that is the "source".


Not necessarily if the model is not in the 'preferred form for modification'.

If I make a film and use a photo from Wikipedia that is licensed under this CC BY-SA license, does my film become a derivative work and therefore must be licensed under CC BY-SA also?


Yes - that's what 'share alike' basically means.

It would make more intuitive sense to me that you would be required to share the photo and any changes you made to it, instead of licensing the entire product or artwork you used the photo in under the same license.


That may be what you want to have, but the license is explicitly designed to deny you that - it says whatever you derive from the work, you must make available under the same license that covers the original work (if you make available at all).

Both GPL and CC-BY-SA are designed to prevent people from using stuff for their works without giving back to the community. So basically GPL is a closed world - you can not take anything from it and create something that is not GPL. If you want a non-GPL product, you can not touch any GPL licensed content.

Try to see it that way - my work is available and open for you to modify and re-distribute as you need - why would I want you to get away with not returning in kind?

(Whether a legal provision is intuitive to anyone is irrelevant anyway...)

That is, if I use CC BY-SA content in a work, a video game, film, collage, slide presentation etc., the entire product must be licensed under CC BY-SA as well?


If you have to abide by the terms of the license and can not claim 'fair use' which basically circumvents copyright and hence also any license - then yes.
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Re: Questions about GPL license

Postby NewFlyer153 » Fri May 31, 2019 8:04 am

Thorsten wrote in Fri May 31, 2019 4:47 am:
(Whether a legal provision is intuitive to anyone is irrelevant anyway...)


I don't feel you needed to make that point. I'm not so stupid that I believe that a law's intuitiveness decides the law's force or applicability. I was telling you about what I felt, not making a legal argument.

Thorsten wrote in Fri May 31, 2019 4:47 am:Try to see it that way - my work is available and open for you to modify and re-distribute as you need - why would I want you to get away with not returning in kind?


Yes, I understand the importance of returning in kind, as you put it. It's the spirit of the endeavor whereby every contribution can be enjoyed by all. But I'm not talking about modifying your sharealike product, such as an artwork. In one example case, do you think it's fair or balanced that an individual or team of producers making a multi-million dollar production such as a film uses a CC BY-SA photograph, and then is obligated to release their entire production whereby anyone can sell and profit from that production? I understand the fairness to the original photographer must be borne in mind also, but the costs, time and effort are entirely disproportionate. Surely if fairness is of paramount consideration in this licensing, I think due consideration should be given to the difference in work and effort between taking a photograph and making large-scale and expensive production lasting years. This is one example that I don't consider fair as far as this Sharealike condition goes, if it's in fact as you say it is.

There are cases where I might tend to agree with it. Undoubtedly if you improve the photo or picture, then the result of that should be made Creative Commons. Even in the case if you use the photograph in a small collage or collection, then maybe that collection should be become Creative Commons also. However some photo someone took shown for a brief interval in a feature-length film invoking the obligation that that entire production become CC doesn't seem fair either.
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Re: Questions about GPL license

Postby bugman » Fri May 31, 2019 8:35 am

Hi, I am Edward. The term infect is used by those either attacking the concept of open source or those wanting to rip it off (take from it without giving back). It is a FUD term that is not accurate. People who contribute to open source keep their ownership of their content. But they wish to have a community working together to build something greater than they can alone. The GPL licence builds such a community, as everyone who expands on the original work must contribute the changes back (the only exception being if you only use it internally for your own personal use).

This is quite simple. The GPL is about preventing others from ripping off your hard work (by falling back to basic copyright law), by requiring derivatives of your hard work to be under the same licence. If person X violates the licence that the original content creator applied to their IP, then the licence is revoked. The result is that person X would be using copyrighted material with zero permission. That is checkmate for person X - any continued distribution of the derivative is an illegal activity.

Regards,
Edward


Edit: If you have used content created by Emmanuel Baranger (Helijah) and are not abiding by the GPL by distributing the whole as GPL, you are in violation of the GPL and you no longer have any licence to use his work. The CC-BY licence works in essentially the same way - you violate its terms and do not distribute the whole as CC-BY and you no longer have a licence to use the content. You would then be using copyrighted material illegally and Emmanuel or others could start legal proceedings against you, in which you have zero chance of winning.
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