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I was wondering what was the appropriate way of distributing Q2A add-ons. In order to tackle this I thought about the following related questions that most developers might come up with:

  1. Does the add-on need to be licensed?
  2. Under what licenses can I distribute my add-ons?
  3. How can I license my add-on under a license compatible with the core?
  4. Can I license my add-ons with a proprietary license?
  5. Can I charge for distributing my add-ons?
  6. If I create an add-on do I have to make the code public?
  7. Can users distribute the add-ons I sent them?
  8. Can users claim the add-ons as if they were their own?
  9. If someones distributes one of my add-ons,
    1. Do I need to be notified?
    2. Are they allowed to charge for that?
    3. Can they change the copyright?
    4. Can they change the code?
  10. Is there any way in which I can distribute my add-on, get the money and make sure no one distributes it for free?
  11. Is it appropriate/well-seen to distribute an add-on which I have received from a developer?
  12. Can I distribute a non-GPL-Compatible add-on which I have not developed?

If you happen to have any question and a clear answer (ideally with a source linking to the Free Software Foundation site) feel free to add them.

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Here is my point of view for each of the questions. I tried to support them with a link to where the answer might come from. However, this is not an exact science so this might lead to discussion, which I think it's OK in order to get a better understanding on what can or can't be done.

1. No. If it is not licensed and most likely not even copyrighted then it would be part of the public domain.

2. The core is licensed under the GPL license. This means that you can license your add-ons only under GPL-Compatible licenses.

   Source: http://www.gnu.org/licenses/license-list.en.html#GPLCompatibleLicenses

3. Follow the steps in here: http://www.gnu.org/licenses/gpl-howto.html

4. No. As the core is GPL it requires any piece of code that uses it to be GPL-Compatible. If your add-ons call the core then they should be GPL-Compatible. If your add-ons share data structures with the core they should be GPL-Compatible. If your add-ons do not work on their own and require the core to operate then they should be GPL-Compatible. Clearly, there is no way to run away from making your add-ons GPL-Compatible as they are considered derivatives of the core itself.

   Source: http://www.gnu.org/licenses/gpl-faq.en.html#GPLAndPlugins and https://en.wikipedia.org/wiki/Proprietary_software

5. Yes, the GPL license allows you to do so.

   Source: http://www.gnu.org/philosophy/selling.en.html and http://www.gnu.org/licenses/gpl-faq.en.html#DoesTheGPLAllowRequireFee

6. No, you don't have to. You can distribute it to anyone you want or not distribute it at all.

   Source: http://www.gnu.org/licenses/gpl-faq.en.html#GPLRequireSourcePostedPublic and http://www.gnu.org/licenses/gpl-faq.en.html#UnreleasedMods

7. Yes. The GPL license allows them to distribute the add-ons to anyone and even charge for that.

   Source: http://www.gnu.org/licenses/gpl-faq.en.html#CompanyGPLCostsMoney

8. Definitely not. Thing is this also includes yourself. This means, the add-ons are by themselves derivatives of the Q2A core. So they have to keep the same copyright as the core. However, you can add yourself as a copyright owner of your add-on but you can not remove anyone from the original work.

9.1. No.

   Source: http://www.gnu.org/licenses/gpl-faq.en.html#DoesTheGPLAllowRequireFee

9.2. Yes.

   Source: http://www.gnu.org/licenses/gpl-faq.en.html#DoesTheGPLAllowRequireFee

9.3. It depends. If they have created a derivative work of your add-on, which is a derivative work of the core, then they can add themselves as copyright owners of the changes they have added. If they have not created any derivative work then they can not touch the copyright.

9.4. Yes, and they can distribute it and even even sell it.

   Source: http://www.gnu.org/licenses/gpl-faq.en.html#GPLCommercially

10. No. The GPL license does not allow you to do so.

   Source: http://www.gnu.org/licenses/gpl-faq.en.html#DoesTheGPLAllowRequireFee and http://www.gnu.org/licenses/gpl-faq.en.html#CanDeveloperThirdParty

11. This question makes no sense at all. It is not a matter of something being appropriate/well-seen or not. It is a matter of violating the license or not. Distribution of an addon (which must be GPL-Compatible) under a GPL-Compatible license does not violate the license at all.

   Source: http://www.gnu.org/licenses/gpl-faq.en.html#CompanyGPLCostsMoney

12. As the add-on is a derivative of the Q2A core which is licensed under the GPL license then it must be licensed under a GPL-Compatible license. If it is licensed under a different license then it is in violation of the GPL license inherited by the Q2A core. Being strict you should report the violation. Being not so strict you could just remove the non-GPL-Compatible license, add the GPL-License and distribute it. Being not strict at all, you could contact the developer and ask them to correct this situation.

   Source: http://www.gnu.org/licenses/gpl-faq.en.html#GPLAndPlugins , http://www.gnu.org/licenses/gpl-faq.en.html#ReportingViolation and http://www.gnu.org/licenses/gpl-faq.en.html#HeardOtherLicense
I see your point and I consider that as a possibility. In any case I think it is a bit off-topic considering the question title :) Probably more suitable for the http://www.question2answer.org/qa/46918 thread
you're right, I made a bad swap :) but both are related somewhere
Just to add, if you make a theme then it's certainly possible to license any custom graphics and "non-essential" assets under a different license such as Creative Commons.
@pupi1985, this is one of the imp QA, after few days it will go away from front page into pool of other QA. then only search can find.

I feel we should come up with new tab similar to activity or questions at top, call it as a pin/faq, only admin should be able to pin all important questions there so that it will be easy for users to see. it will be quick ref. admin should be able to mark any question and move up or down depending on priority.

what do you think? or any other solution for this?