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by dj43nq 2844 days ago
Don’t you end up with licensing fees if you use QT in a commercial product? Seems like a downside to me.
3 comments

QT seems interesting.

For those like me who’ve never used QT: As long as you don’t statically link the QT libraries you don’t have to open source your entire commercial application. I’m not a lawyer.

General notes about licensing https://www1.qt.io/licensing/

Comparison of licenses https://www1.qt.io/licensing-comparison/

> As long as you don’t statically link the QT libraries you don’t have to open source your entire commercial application

I provided a link from the FSF that shows that this is not the case just below - you can statically link proprietary apps with LGPL qt.

“(1) If you statically link against an LGPL'd library, you must also provide your application in an object (not necessarily source) format, so that a user has the opportunity to modify the library and relink the application.”

So for LGPL. As a commercial application developer I’m not sure I’d want to do that. I’d then have to field support requests for that object file.

Still, good to know.

Not at all. You have to respect the license of Qt (e.g. if your customer asks you for the source of the Qt libraries you have to provide them - including any modification you made to them), but you can keep your own app proprietary and ship the whole however you like.
LGPL isn't that hard to comply with for a desktop application, so no.
With LGPL, you can't statically link the library though. Which requires your user to install it manualy, unless you package your software with some kind of installer (which is not so common on windows for cli executables).
> With LGPL, you can't statically link the library though.

no, that's tiresomely false. You can link proprietary code statically with LGPL code. LGPL does not give a shit about static or dynamic libraries because LGPL is not a language-specific license.

Right from the source: https://www.gnu.org/licenses/gpl-faq.html#LGPLStaticVsDynami...

Thanks for the link. The nuance I was missing is that you can distribute statically-linked LGPL library as long as you provide a way for your user to override the chosen library with his own version of the library.
It's very common to ship windows CLI tools as a .zip file with an exe and a bunch of .dlls, that's not exactly burdensome to install compared to only an executable.