I think it's because Qt has traditionally had a pretty weird dual- or tri-licensing model: https://www.qt.io/faq/#_Toc453700684 https://www.qt.io/faq/#_Toc45370

I think it's because Qt has traditionally had a pretty weird dual- or tri-licensing model: https://www.qt.io/faq/#_Toc453700684 https://www.qt.io/faq/#_Toc453700684 which resulted in less adoption by developers because of the viral nature of the GPL. IIRC, it used to be that even the core Qt libs were GPL (unless you paid for a commercial license), while now most (but still not all) libs are also available under the LGPL. GTK has always been plain LGPL 2. Nothing scary.