Obsolete. Nowadays qt libs are distributed on choice between commercial and lgpl

Some language bidings still come in GPL only.

Don't you have to release the source code of your application if you don't want to pay?

No. That's GPL, not LGPL.

Not if you dynamically bind with qt libs. But yes you have to, if you statically bind with qt libs.

Can the licensing be an issue on Android or iOS?

I still haven't found a clear answer to that, but using the LGPL license could pose a problem, because you need to allow the user to recompile the application with his own version of Qt. On iOS shared libraries are not allowed on the store, so you should distribute the files for static linking... it becomes quite messy and sort of unclear from the legal point of view.

Even if it's wasn't clear before now it's pretty clear - you must buy commercial license if you want to be on App Store. There was Qt license change[1] in January 2016 and there is no longer LGPLv2.1 licensed version since Qt 5.7.

Only option for commercial software currently is LGPLv3 and it's doesn't allow tivoization.

[1] https://subsurface-divelog.org/2016/02/subsurface-mobile-for...

Hey thanks. I wasn't aware of the dylib appstore restriction. Is this still the case with iOS8 and if not, could a dynamic LGPL Qt app be put on the store. I hope they allow this going forward.

Qt open source license is perfectly compatible with Android / Google Play, but not OS X / App Store.