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I'm a developer working for an automotive company and I'm currently developing a hardware testing tool which includes a graphical user interface built on the QT framework. The application will solely be used by employees of our company and is not intended to be sold to external customers. My question is, do I need a commercial license for the framework even though I don't want to sell the software and the source code is free for all employees of the corporation?

Thanks in advance

Alex

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4 Answers 4

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My question is, do I need a commercial license for the framework even though I don't want to sell the software and the source code is free for all employees of the corporation?

No.

As long as you can comply with the (L)GPL requirements of the Qt libraries, then you do not need to purchase a "commercial license" from the Qt Company. Note that the terminology "commercial license" is a bit ambiguous, because the (L)GPL license also allows 'commercial' use as long as you can follow the obligations. Namely, the obligation for the LGPL is that you distribute the source code of the LGPL libraries themselves (i.e. the Qt libraries), and also that you allow your users to replace the LGPL libraries with alternative versions.

Basically what this has been interpreted to mean is that if you distribute LGPL libraries (such as Qt) with your application, then you also must:

  1. Distribute to your users the source code of the same version of that library, or make it available in a way that is conformant with the LGPL license.

  2. Make it possible for a user to use a different version of that LGPL library with your application. In practice this means that you must use dynamically linked libraries for the LGPL library (i.e. on Windows, the Qt libraries must be DLLs, and on Linux the libraries for Qt must be .so's).

In practice it also means that on platforms like iOS and Android, LGPL is not really usable (because these platforms apparently do not allow users to replace the libraries with another version). Basically, the LGPL requires that you document the process for replacing your version of the LGPL library (Qt) with another version that the user may have built herself.

See: LGPL

Note that some components of the Qt framework may be GPL licensed, and not LGPL. If you don't want to release the source code of your whole application, you must avoid distributing GPL applications in a way that combines it with your application. To be safe it would be best not to distribute the GPL components at all together with your application.

See also: Can I use an LGPL-licenced library in my commercial app?

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  • "or make it (source code) available in a way that is conformant with the LGPL license." What does it mean in practise ? We need to provide github link of Qt in readme.md file or about dialog?
    – Jcyrss
    Oct 10 at 14:31
  • @Jcyrss Normally, you must provide the source code yourself. If you supply a Github link, then technically that might be OK, but it should be a repo you control, and you should also be supplying your binaries there as well. If you look at the (L)GPL, it says that if you offer it online, then you must offer it "from the same place". So, to me that means that both binaries and sources must be offered on Github if you decide to do it that way. Note that you have to provide your version of Qt that you used, i.e. the same exact version. Linking to the official Qt repo is probably not sufficient.
    – Brandin
    Oct 11 at 6:07
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No, you don't need a commercial Qt license if you don't distribute your application.

If the code you write for this application is owned by your employer and is only provided to your colleagues to assist them in their work duties, then the application is not being distributed according to copyright law. This means that the requirements of the LGPL license don't trigger and you have no obligations to comply with those requirements.

If the application gets distributed to a different legal entity (this could be within the same corporation, depending on how it is legally organized!), then you either need to comply with the LGPL requirements or you need to buy a commercial license.

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NO. You can use open source Qt. I think you can use GPL components too. If you want to sell your closed source software, then you can use only LGPL Qt.

https://www.gnu.org/licenses/gpl-faq.html#InternalDistribution

You can use LGPL Qt for a closed source project, but you must comply the LGPL requirements. It's hard, but not impossible.

The easy way: you can use this QT LGPL app template:

https://marketplace.qt.io/products/qt-lgpl-app-template

and add the "about" dialog in your app.

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  • Thank you for posting about the App Template. I didn't know about that :) Except, when I go to purchase it I'm getting: "The page you were looking for doesn't exist. You may have mistyped the address or the page may have moved." Windows 10, Chrome.
    – Daniel Donnelly
    May 30, 2021 at 15:24
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    I think you need a Qt account to buy extension.
    – Miguel Angel Pons
    May 31, 2021 at 16:21
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Yes

You are using it in your business - that’s a commercial application. It doesn’t matter that your business is cars, not software.

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  • I know very little about open source licensing, but I have a question. I thought that open source licensing required only that the source code be distributed with the application. Couldn't this requirement be met within the OP's corporation? Is there a restriction against creating an application with an open source license, while intending not to distribute that application outside the corporation?
    – James
    Sep 9, 2019 at 12:32
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    To clarify my comment, is there really a restriction against using an open source license for commercial purposes? I thought that was fine as long as the source code was distributed with the application.
    – James
    Sep 9, 2019 at 13:03
  • As I understood Qt's licensing, you are allowed to license your application seperately from the Qt part as long as you stick to dynamic linking and you have the obligation to share the Qt source code and any changes made to it. And all of this by just using the open source license.
    – WoodenGolem
    Sep 9, 2019 at 18:58
  • @WoodenGolem Different parts of Qt have different open source licenses. No open source license forbids commercial use, though many licenses have clauses that make commercial use unattractive (e.g. having to provide some or all source code to end users). In your case the end user would be your company, so no source disclosure obligations exist for GPL/LGPL licenses. For details about how open source licenses work, consider asking on Open Source.
    – amon
    Sep 9, 2019 at 19:25
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    Yes it is true that this is a "commercial" application, but this answer feels like it comes from someone who has never even skimmed the GPL or LGPL, both of which explicitly allow 'commercial' applications as well, as long as you follow the obligations of those licenses. See also Can I use an LGPL-licenced library in my commercial app?.
    – Brandin
    Sep 17, 2019 at 7:54

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