Qt Commercial License Terms, Independent Developers
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@luca
You might look at the overview in, say, https://en.wikipedia.org/wiki/GNU_Lesser_General_Public_License:The license allows developers and companies to use and integrate software released under the LGPL into their own (even proprietary) software without being required by the terms of a strong copyleft license to release the source code of their own components.
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wrote on 23 May 2018, 13:23 last edited by JonB
@luca
I am not an expert, but I believe I know of three differences:- Yes, you cannot statically link without a license. (And I have a feeling that by definition this may exclude [certain?] mobile devices because they don't do shared libraries.)
- I believe there are a few Qt components which are not in the Community Edition but are in the Commercial.
- Although I pointed out above that the LGPL does not require source code publication, it does have alternative, lesser restrictions, e.g.:
The license only requires software under the LGPL be modifiable by end users via source code availability. For proprietary software, code under the LGPL is usually used in the form of a shared library, so that there is a clear separation between the proprietary and LGPL components.
You may avoid this requirement by purchasing a commercial license.
Please take what I write with a pinch of salt. As I say, I am not an expert, and the advice given in this forum for this issue is to read the T&Cs carefully. I am just suggesting some avenues you may wish to investigate further.
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@luca
I am not an expert, but I believe I know of three differences:- Yes, you cannot statically link without a license. (And I have a feeling that by definition this may exclude [certain?] mobile devices because they don't do shared libraries.)
- I believe there are a few Qt components which are not in the Community Edition but are in the Commercial.
- Although I pointed out above that the LGPL does not require source code publication, it does have alternative, lesser restrictions, e.g.:
The license only requires software under the LGPL be modifiable by end users via source code availability. For proprietary software, code under the LGPL is usually used in the form of a shared library, so that there is a clear separation between the proprietary and LGPL components.
You may avoid this requirement by purchasing a commercial license.
Please take what I write with a pinch of salt. As I say, I am not an expert, and the advice given in this forum for this issue is to read the T&Cs carefully. I am just suggesting some avenues you may wish to investigate further.
wrote on 23 May 2018, 13:47 last edited by@JonB So in your opinion the point of this thread (from the beginning) simply doesn't exist...
Developing at least for Android you dynamically link to Qt so no static link (no need of license).For me it should be great but I'm not sure about that.
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wrote on 23 May 2018, 14:23 last edited by
A requirement of LGPL is that users must be able to replace the LGPL component (Qt) with their own version so you should make sure you don't break binary compatibility (for example using the private Qt modules)
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@JonB So in your opinion the point of this thread (from the beginning) simply doesn't exist...
Developing at least for Android you dynamically link to Qt so no static link (no need of license).For me it should be great but I'm not sure about that.
wrote on 24 May 2018, 07:36 last edited by@luca
Although I would not be encouraging you to not pay for Qt if you can:If you link dynamically to Qt, use only LGPL components, do not use private Qt modules or otherwise tinker with the Qt side, and there is nothing special about Android (I think it used to require static linking maybe, but not now) or whatever "app stores" you use, my understanding is that you do not need a commercial license.
Basically, LGPL does not require you to publish your own source code when you link against an LGPL component, even if your app is commercial/you make money out of the LGPL usage. However, in my own case I use PyQt (Python binding to Qt), and that is GPL rather than LGPL, so I do have to make my source available if I distribute.
All statements above according only to my understanding.
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@luca
Although I would not be encouraging you to not pay for Qt if you can:If you link dynamically to Qt, use only LGPL components, do not use private Qt modules or otherwise tinker with the Qt side, and there is nothing special about Android (I think it used to require static linking maybe, but not now) or whatever "app stores" you use, my understanding is that you do not need a commercial license.
Basically, LGPL does not require you to publish your own source code when you link against an LGPL component, even if your app is commercial/you make money out of the LGPL usage. However, in my own case I use PyQt (Python binding to Qt), and that is GPL rather than LGPL, so I do have to make my source available if I distribute.
All statements above according only to my understanding.
wrote on 24 May 2018, 20:22 last edited by@JonB Thanks for the explanation.
I would like to pay for a commercial Qt license to thanks for the good works THEY did, but at the moment it cost too much for free projects (non open source).
The startup plan is not so expensive but it require you to pay forever if you publish your app in an app store.I hope Qt will find a good solution for all...
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@JonB Thanks for the explanation.
I would like to pay for a commercial Qt license to thanks for the good works THEY did, but at the moment it cost too much for free projects (non open source).
The startup plan is not so expensive but it require you to pay forever if you publish your app in an app store.I hope Qt will find a good solution for all...
wrote on 24 May 2018, 23:42 last edited byI hope Qt will find a good solution for all...
They did, LGPL. :) You can use that with a closed source free application on a web store as long as you link dynamically and Qt can be replaced easily with a version built elsewhere.
Since you can now link dynamically on both iOS and android you should have no issues using the LGPL license for Qt. LGPL was made for your exact use case.
Disclaimer: IANAL make sure to check with a lawyer.
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I hope Qt will find a good solution for all...
They did, LGPL. :) You can use that with a closed source free application on a web store as long as you link dynamically and Qt can be replaced easily with a version built elsewhere.
Since you can now link dynamically on both iOS and android you should have no issues using the LGPL license for Qt. LGPL was made for your exact use case.
Disclaimer: IANAL make sure to check with a lawyer.
wrote on 25 May 2018, 07:33 last edited by@ambershark said in Qt Commercial License Terms, Independent Developers:
Since you can now link dynamically on both iOS and android
Ah, right, is that what I was thinking I recalled when I wrote
I think it used to require static linking maybe, but not now
? Have they made it so you can now but didn't used to be able to? OOI, is that a change at the Android side or the Qt side to make it possible?
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wrote on 25 May 2018, 07:54 last edited by
Where can I find a list of LGPL Qt modules for a specific release of Qt ?
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@ambershark said in Qt Commercial License Terms, Independent Developers:
Since you can now link dynamically on both iOS and android
Ah, right, is that what I was thinking I recalled when I wrote
I think it used to require static linking maybe, but not now
? Have they made it so you can now but didn't used to be able to? OOI, is that a change at the Android side or the Qt side to make it possible?
wrote on 25 May 2018, 08:20 last edited by@JonB Pretty sure android always supported dynamic linking, although I could be wrong here, I'm not really a mobile developer. I've done one back end library on mobile and that was it.
It was iOS that used to be static only and change to allow dynamic linking recently (like last year or 2).
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wrote on 4 Dec 2019, 11:38 last edited by
I am an independent game author. If I use LGPL, develop a library that uses QML and dynamically links QT, and then publish it to steam, do I need to pay QT or open source?
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I am an independent game author. If I use LGPL, develop a library that uses QML and dynamically links QT, and then publish it to steam, do I need to pay QT or open source?
@Cheng-shi-hua said in Qt Commercial License Terms, Independent Developers:
do I need to pay QT or open source?
No, as long as you can fulfill LGPL3 you do not need commercial license and do not have to open your source code.
LGPL3 requires you to provide users the possibility to replace Qt libraries with their own versions. This usually requires you to provide object files (.o), so users can relink. And it is not possible when using static Qt libraries!Keep in mind people here (me included) are not lawyers!
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wrote on 4 Dec 2019, 12:34 last edited by
No QT official came out to clarify? This matter is important
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No QT official came out to clarify? This matter is important
@Cheng-shi-hua This forum is for Qt users and not "Qt officials". If you want an answer from Qt officials then pleas ask Qt Company.
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wrote on 4 Dec 2019, 13:15 last edited by
This is the case, thank you very much. Since it is a community, you can advertise here when I develop a game :)
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Bannedwrote on 7 Nov 2022, 10:33 last edited by Betty R. Harris 11 Jul 2022, 10:35This post is deleted!
