[brcha]

Qt is LGPL. So there are no limitations unless you make changes to the Qt library (which you probably won't do). If you do make changes, though, then you would have to release them under LGPL license.

So, I think there are absolutely no limitations to using Qt LGPL in a commercial application. All you get from the commercial license is support.

Note: I'm not a lawyer, don't hang me if you get sued or something. But I do think I'm right about this.

[chrisseaton]

> there are no limitations unless you make changes to the Qt library

I thought you were required to allow linking to a newer or modified version of a LGPL library? So one limitation is you have to either dynamically link or provide a mechanism to relink.

[purplesinha]

IANAL, but this requirement is the reason I stopped using Qt for my own projects. Those terms would seem to mean anything you write using Qt can't be deployed on a closed platform. Tons of people use LGPLd code on iOS and Android (stores like Play and Amazon) though and I think most users and developers are ignorant of the relinking requirement. I didn't want to risk it.

[rectang]

The Apache Software Foundation does not allow its projects to have mandatory LGPL dependencies for this reason: it would become impossible to bundle the Apache product plus its dependencies into a package that forbids modification, either through technical or licensing restrictions.

This linking restriction is not a part of other product-scoped copyleft licenses like the MPL and the EPL.

[rsynnott]

Here's an old example of how it can (apparently; presumably according to Google's lawyers) be done for iOS: https://news.ycombinator.com/item?id=4302517

Google has now killed off Sparrow entirely, but they used to make it available for download so that an end-user could in principle re-link it, to comply with the LGPL.

[ChajusSaib]

So if I were to statically link my application but release the object files and let user's re-compile it with another version of the library then that would satisfy the LGPL license? If so I think I might be headed back to Qt.

[paxcoder]

Seems so: https://www.gnu.org/licenses/gpl-faq.html#LGPLStaticVsDynami...

It would appear that once again the FUD is unjustified, and in reality GNU/SFLC licenses well made

[chrisseaton]

Or just dynamically link.

[ChajusSaib]

I'm asking for iOS which won't allow it.

[chronial]

> Those terms would seem to mean anything you write using Qt can't be deployed on a closed platform.

This sentence is missing a "closed source". If you license your application under GPL, you will have none of these problems.

[brcha]

Yes, if you link dynamically, you are generally okay with just sending your executables.

If you link statically, you also have to make your object code available for relinking if needed. But that generally comes down to doing something like "ar q libMyApp.a *.o" and then the user would make the app with "gcc -o MyApp libMyApp.a -lQtWhatever".

If you distribute as some package (like .apk for android), you'd have to make it possible for user to change the library. Simply allowing users to download .apk files would make it work, since they can unzip them, change the library and rezip them back.

So, I wouldn't really call those "limitations". Just pesky things you have to do if making a commercial app with lgpl lib.

Oh, and there is no requirement to link with a newer version of the library, to the best of my knowledge. That's generally impossible since newer versions might (and do) deprecate features that were available in the older versions.

[Matthias247]

It's also in the meantime LGPLv3 - at least for certain QT components, but the system is not easy to understand. The v3 requirements add that if you distribute an application (or device) with it, you have to provide the user with a way to update the linked QT library with a different version that he provides himself.