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Qt license questions

1 points by ilSignorCarlo ↗ HN
Hi, I'm working on a commercial software in c++ a Qt with other two developers.

We need to sell the software and distribute it with closed source.

We have just some doubts abot the Qt license. The commercial one costs just too much for us, so it is excluded. The GPL require that we distribute the source code.

What about the LGPL? Are we able to keed the source closed and sell the software? Which are the restrictions? I've read something about static linking, but I'm not sure what it means.

Thanks for your help, Carlo

2 comments

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mcav
With the LGPL, you can keep your own code closed-source, but you must dynamically link the QT library. That means that your program must require QT's DLL file to run. If your program still works without QT's DLL file present on your system, you've statically linked it, which you cannot do with the LGPL.

The rationale behind it is that your end-users should be able to use a different QT DLL instead -- e.g. if they wanted to recompile QT themselves and use their compiled version with your program.

(IANAL)

yosh
That's inaccurate, you can statically link closed source to an LGPL library, as long as you provide the object files so the user can relink it against a modified version of the LGPL library.