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49

If your plugin is a derivative work of the GPL-covered software, then you can only publish/share/distribute your plugin under the terms of the GPL. It is not clear when a plugin is a derivative work. It seems to be the belief of the FSF (the GPL authors) that the following aspects can indicate derivativeness: the plugin is designed to be combined with a ...


11

Maybe. Yes, you have to comply with the terms of the host application's license. However, a copyleft platform can choose to go either way. Some copyleft applications have a specific licensing exemption for plugins; in other cases, the technical architecture does not result in a derived work and thus an obligation. Consider a plugin architecture where a ...


11

Since you explicitly say the plugin runs as a separate process from the closed-source program, the FSF presents the legal opinion that a plugin would probably be a separate work from the original (emphasis mine): Can I apply the GPL when writing a plug-in for a non-free program? If the program uses fork and exec to invoke plug-ins, then the plug-ins are ...


7

Fortunately, this is not a tricky case at all. You are not in any way bound by any terms in the GPL if you are not distributing software that is licensed to you under the GPL. Neither you nor your users are distributing software licensed to them under the GPL. Your users are always free to use free software in any way they like. The GPL doesn't forbid - in ...


6

To answer the question of the form "You've created a plugin for X with GPL'd libraries; can you force X to be open sourced?" -- absolutely not. Instead, what may be true (see the final paragraph for the corresponding "might not") is that that plugin cannot be legally distributed in combination with the main program unless the main program is also under the ...


5

Can I write a plugin to interface the closed-source software with the GPL library, for my private use? Yes, the GPL does not affect private use. This is both due to private use exception in copyright law, and because the GPL explicitly says that it only applies to distributions of "something" containing GPL code. Can I distribute the plugin as a ...


5

IANAL/IANYL. That said, the devil, as usual, is in the details, and you don't give us much information about how these adaptors work. If, for example, the B-C adapter is a piece of software that works by linking against libraries that form part of B, and also against libraries that form part of C, then you've created a single, large, derivative work of ...


5

The GPL's principal obligations, those governing source distribution and GPL-covers-all, apply only when the program is itself distributed, rather than used. As long as neither you nor anyone else distributes the program and the plugin together, there will be no GPL violations occasioned; certainly not by those choosing to obtain the parts separately and ...


5

If I use a compiled program [...] which is under a license that everyone has the rights to use and sell (Eg: GPL) [...] and then I want to develop an extended feature for it [...] to be sold for money, to be available only to the person that paid for this premium feature - Must I release this premium feature also as GPL? If your work is a derivative of the ...


4

The existing answer is perhaps not clear enough. A third party cannot force the GPL on you. This is not specific to the GPL. They couldn't force a BSD or closed-source license on you either. Imagine if it was possible. Microsoft would need to create one closed-source program and have the Linux kernel run it, to close down Linux ! And vice versa you could ...


4

The answer is: A host application's license apply to plug-ins written for it if the License is a Copyleft License (such as the GNU GPL), and you distribute the plugin with the application (so no private use exception apply). (The same rules do not apply for a permissive license such Expat (MIT), but your question specifies Copyleft.) Drupal is a CMS that ...


4

The wording "should" is a dead giveaway. The FSF would generally like you (and everybody else) to comply with their ideology but they have no real means of forcing you, in general. That's not necessarily a bad thing because although it's a bit quixotic, the FSF ideology isn't bad. In general, you are legally bound to comply with all terms that anyone (not ...


3

TL;DR: Keeping your library closed source will violate the GPL. As already mentioned in the comments, your question is answered by the FAQ: If the main program and the plugins are a single combined program then this means you must license the plug-in under the GPL or a GPL-compatible free software license and distribute it with source code in a GPL-...


3

No, what you propose is not legal. The LGPL license is written in such a way that the linking exception only works one way. All the code that an LGPL library depends on must be under a GPL-compatible open-source license Code that depends on an LGPL library may use a GPL-incompatible license. The fact that the LGPL library gets used by a GPL application is ...


3

You intend to make a "plugin for a plugin" for Wordpress, where the plugin you're writing code to connect to is itself GPLv2, and you wish to know what your licensing obligations are. The short answer is that GPLv2 s2b says that You must cause any work that you distribute or publish, that in whole or in part contains or is derived from the Program or any ...


3

My first question was whether FileBird was really under GPLv2; they don't exactly go out of the way to make the license a salient. But after some digging it looks like you're right. That given, what you propose - removing the billing and registration hooks - is completely lawful. You don't even have to use another name, though it would probably be kind of ...


3

The traditional way to think of a shared address space is when you have a process that isolates memory regions. This of course would not apply to an OS that does not have a notion of a process. But would not FreeDOS allocate separate memory regions to each of the TSR? Actually the FreeDOS wiki is quite clear and explicit on this topic: Additionally, ...


3

The software is under an open source license, which per the open source definition guarantees you may use it for whatever purpose you want. The license used is the GPLv3, which is a strong copyleft license. It requires that if you distribute your software that includes this plugin, or make a derivative work based on this plugin, the entire work must be ...


3

Yes unless you specify otherwise. The plugin is derived from the API which specifies which functions the plugin needs to export and what they should do. If you released X under GPL you can add an exemption for the plugins and dual license the API itself with a less restrictive license that allows non-GPL license for the plugin. That way you can allow ...


3

Most of these questions have not been decided in the courts, and it's anyone's guess how they would be decided if the question came up. A lawyer's guess might be better than yours, or it might not; the language in the FSF licenses is so vague technically that I certainly wouldn't want to hazard a guess myself. So it comes down to what risks you are ...


3

Let's say I develop a plugin for third-party application X. My plugin has a non-free license, and is commercially distributed. I don't distribute application X. Okay. That would require that your plugin not be a derivative work of any work covered by the GPL. That means that it cannot contain sufficient protectable expression from the work that is covered ...


2

Yes. Many open source CMS projects cover this in their FAQ, Drupal and Wordpress being two notable instances. The Drupal FAQ #7 states that plugins are derivatives of the original; the Wordpress Support forums tell you the same thing. From there, it just depends on how the original is licensed. Wordpress is under the GPL, so derivative works must also be ...


2

The readme file of the project declares the project under the GPLv3. Be wary, anything that uses it is forced to be under the GPLv3 as well. This is a strong copyleft license. Warning call! The project however, doesn't actually include a license file, thereby making the project improperly licensed, and the GPL then legally doesn't apply to the project (if ...


2

Yes, you can achieve your goal with the GNU GPL, except for prohibiting commercial use. Section 7 of the GNU GPL states that you may add "additional terms" as long as they do not restrict the rights granted by the GNU GPL. In your case, you want to grant an additional exception from the conditions in the GNU GPL or at least clarify your point of view. So ...


2

I am not a lawyer, but here is my two cents. Although the GPLv3 strongly recommends that you include a comment header declaring the license and the copyright information in each individual file, I don't believe it's required. https://www.gnu.org/licenses/gpl-howto.en.html Unless stated otherwise in individual files, I would say the project as a whole is ...


2

The method of communication is not relevant. If you don't modify the GPLv2 program, and your proprietary program is developed independently from the GPLv2 program, there is no derivation work, so you can use the GPLv2 program without restrictions. If you modify the GPLv2 program, things are grey. On both side you will have to code the communication part, ...


2

I believe requiring .js files is definitely a dynamic linking. It's not much different from linking a library in your project for the use of library's functionality, which would be considered using the library as a plugin by GPL: Linking a GPL covered work statically or dynamically with other modules is making a combined work based on the GPL covered work....


2

Tough question. I'd say that if the the plug-in does not use code from your software, then it is not a derivative work but a good lecture can be this: https://www.drupal.org/about/licensing, where there is a good explanation (Drupal call the plugin "module") about the topic.


2

Your question implies four things that you want to do. I will list each one you want to do and analyze whether they are allowed by the license(s): Release GPL_APP with full source-code. This is completely in accordance with the GPL. Patch GPL_APP to look for a proprietary library and use it if available. This is possibly allowed. See the GPL FAQ "Can I ...


2

If this is an application you are developing, there's no problem: as the copyright holder, you can do whatever you like. If you want to permit other people to develop closed-source plugins for your application, it's recommended that you add an exception clause to your license statement (eg. "Plugins for MyApplication that use the documented plugin API can ...


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