KDE is based on Qt which was a commercial library back then. It was licensed for free under the GPL (not LGPL!) or you could buy a commercial license from Trolltech.
That caused all kinds of licensing problems (not only for commercial applications, but if you did a Qt GUI app your only choice was the GPL, no other license) which drove people towards gtk.
That's ancient history, but the Qt situation isn't much better now.
First Nokia bought Qt and relicensed it as LGPL, because they needed it to be used by as many people as possible to gain users for their mobile platform. Then Nokia couldn't decide what mobile platform to use, then Elop happened and Nokia basically died.
Today Qt is still partially LGPL but was spinned off as Digia that is trying very hard to make money out of it. To the point of threats on the page that lets you download the LGPL version, commercial only plugins, and unaffordable pricing for small companies and hobbyists.
Agree that gnome still looks like Apple envy.