Using qt for a commercial application on windows (LGPL)
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@Jo-Jo It doesn't matter how you store the source code. What is required is that you can provide Qt source code to whoever asks for it. It does not have to be an URL, it can also be an USB stick or what ever.
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@jsulm Do you mean to provide the Qt source code on demand? But am I not obliged to provide access to the Qt source code even without user requests?
@Jo-Jo said in Using qt for a commercial application on windows (LGPL):
But am I not obliged to provide access to the Qt source code even without user requests?
You are as far as I know, read again what @SimonSchroeder wrote
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@Jo-Jo said in Using qt for a commercial application on windows (LGPL):
But am I not obliged to provide access to the Qt source code even without user requests?
You are as far as I know, read again what @SimonSchroeder wrote
@jsulm I have read it. As far as I understand, I am obliged to provide a download link plus a guarantee that if the link stops working, I will be able to transfer the Qt sources in an alternative way. To do this, I must store the Qt sources somewhere on my own. Right?
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@jsulm I have read it. As far as I understand, I am obliged to provide a download link plus a guarantee that if the link stops working, I will be able to transfer the Qt sources in an alternative way. To do this, I must store the Qt sources somewhere on my own. Right?
@Jo-Jo said in Using qt for a commercial application on windows (LGPL):
To do this, I must store the Qt sources somewhere on my own.
Yes, that's what I wrote
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@Jo-Jo said in Using qt for a commercial application on windows (LGPL):
To do this, I must store the Qt sources somewhere on my own.
Yes, that's what I wrote
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Yes, with the software. Also
QMainWindowQApplication has an aboutQt method that shows this information. -
Yes, with the software. Also
QMainWindowQApplication has an aboutQt method that shows this information.@SGaist
I can't find the QMainWindow::aboutQt method in the documentation. Can you provide a link? I found QApplication::aboutQt but it gives us general information about Qt licensing (not specific to LGPL)One more question: can anyone provide me with a link to a commercial Windows application that uses Qt under the LGPL license? I need such a program as an example
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@SGaist
I can't find the QMainWindow::aboutQt method in the documentation. Can you provide a link? I found QApplication::aboutQt but it gives us general information about Qt licensing (not specific to LGPL)One more question: can anyone provide me with a link to a commercial Windows application that uses Qt under the LGPL license? I need such a program as an example
@Jo-Jo My bad it was QApplication::aboutQt
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@SGaist
I can't find the QMainWindow::aboutQt method in the documentation. Can you provide a link? I found QApplication::aboutQt but it gives us general information about Qt licensing (not specific to LGPL)One more question: can anyone provide me with a link to a commercial Windows application that uses Qt under the LGPL license? I need such a program as an example
@Jo-Jo said in Using qt for a commercial application on windows (LGPL):
can anyone provide me with a link to a commercial Windows application that uses Qt under the LGPL license? I need such a program as an example
I dont know which type of license does Viber use. I cant find any information about licenses inside this application but I see a bunch of Qt`s dlls here
C:\Users\username\AppData\Local\Viber
No Qt mention as well
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@Jo-Jo said in Using qt for a commercial application on windows (LGPL):
can anyone provide me with a link to a commercial Windows application that uses Qt under the LGPL license? I need such a program as an example
I dont know which type of license does Viber use. I cant find any information about licenses inside this application but I see a bunch of Qt`s dlls here
C:\Users\username\AppData\Local\Viber
No Qt mention as well
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@zvoopz said in Using qt for a commercial application on windows (LGPL):
No Qt mention as well
Probably they are using commercial license but I am interested in example of app which releases under LGPL (no payment for Qt license, but commercial app)
@Jo-Jo said in Using qt for a commercial application on windows (LGPL):
I am interested in example of app which releases under LGPL (no payment for Qt license, but commercial app)
I think it might be hard to tell, because to know this, you have to get the source code, which commercial app developers would not publish.
And AFAIK commercial Qt users can link Qt statically while keeping the code hidden. So as "customer" you are not able to tell whether such app even uses Qt.
Meanwhile, commercial LGPL developed apps you also have to buy first to inspect the files that are shipped with it.
(I don't have any apps I paid for, that were developed using Qt)You could check the Windows App Store. Maybe there you find apps tagged with "Qt" (if there is such feature).
Or look into the Showcase subforum here. Maybe you find links to commercial apps that were developed by open source users here in the forum. -
@Jo-Jo said in Using qt for a commercial application on windows (LGPL):
I am interested in example of app which releases under LGPL (no payment for Qt license, but commercial app)
I think it might be hard to tell, because to know this, you have to get the source code, which commercial app developers would not publish.
And AFAIK commercial Qt users can link Qt statically while keeping the code hidden. So as "customer" you are not able to tell whether such app even uses Qt.
Meanwhile, commercial LGPL developed apps you also have to buy first to inspect the files that are shipped with it.
(I don't have any apps I paid for, that were developed using Qt)You could check the Windows App Store. Maybe there you find apps tagged with "Qt" (if there is such feature).
Or look into the Showcase subforum here. Maybe you find links to commercial apps that were developed by open source users here in the forum. -
BTW, any app needs to comply with the same rules when using Qt under the GPL or LGPL. It doesn't matter if it's commercial or not. As soon as you distribute a binary (even if it is open source) you need to follow these rules. So, open source apps using Qt will suffice as example. Just note that just because someone else isn't doing something (e.g. not providing a download link for the Qt sources) doesn't mean this is the correct way to do it.
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BTW, any app needs to comply with the same rules when using Qt under the GPL or LGPL. It doesn't matter if it's commercial or not. As soon as you distribute a binary (even if it is open source) you need to follow these rules. So, open source apps using Qt will suffice as example. Just note that just because someone else isn't doing something (e.g. not providing a download link for the Qt sources) doesn't mean this is the correct way to do it.
@SimonSchroeder said in Using qt for a commercial application on windows (LGPL):
It doesn't matter if it's commercial or not
I disagree with this statement. As far as I know as commercial user you do not have to follow GPL/LPLG as you get Qt under commercial license, not GPL/LGPL (dual licensing).
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@SimonSchroeder said in Using qt for a commercial application on windows (LGPL):
It doesn't matter if it's commercial or not
I disagree with this statement. As far as I know as commercial user you do not have to follow GPL/LPLG as you get Qt under commercial license, not GPL/LGPL (dual licensing).
@jsulm said in Using qt for a commercial application on windows (LGPL):
@SimonSchroeder said in Using qt for a commercial application on windows (LGPL):
It doesn't matter if it's commercial or not
I disagree with this statement. As far as I know as commercial user you do not have to follow GPL/LPLG as you get Qt under commercial license, not GPL/LGPL (dual licensing).
I think @SimonSchroeder meant that when using Qt under GPL/LGPL, the fact that the application is commercial or open source does not change anything with regard to respecting these licenses constraints.
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So, guys, what should I do then? We don't have an example on hand that would prove that all these messages in this topic work effectively in practice. I'm tormented by the question: what if it turns out that following all these rules is not enough to use qt for free? After all, we don't have real examples of anyone who did this and didn't have any problems
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So, guys, what should I do then? We don't have an example on hand that would prove that all these messages in this topic work effectively in practice. I'm tormented by the question: what if it turns out that following all these rules is not enough to use qt for free? After all, we don't have real examples of anyone who did this and didn't have any problems
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So, guys, what should I do then? We don't have an example on hand that would prove that all these messages in this topic work effectively in practice. I'm tormented by the question: what if it turns out that following all these rules is not enough to use qt for free? After all, we don't have real examples of anyone who did this and didn't have any problems
@Jo-Jo said in Using qt for a commercial application on windows (LGPL):
After all, we don't have real examples of anyone who did this and didn't have any problems
I think we don't have any real example where someone did have problems. It is quite rare that companies get sued over open source licenses. Most of the time it is because they are trying to hide that they are using open source components because they don't want to comply with open source licenses (e.g. tivoization). It is also mostly large companies that get sued because they don't think they have to follow the rules. I don't think you'll get sued if you are trying your best to fulfill open source licenses (though legally speaking "doing your best" is not enough). The major problem in correctly answering your question is that there is no legal precedent how to comply with the LGPL. If you ask Qt they will always tell you that they don't know (it's because there is no legal precedent) and they'll offer you a commercial license to be on the safe side.
I'd always choose the LGPL (even for a commercial application). The way I am using Qt I don't see any advantage in a commercial license. The only good thing about the commercial license is peace of mind. But, it is a little expensive for that (especially if you have multiple developers on the project; even more so, if some developers just occasionally program a small part of the software like two weeks a year).
