I'd been hoping this might happen ever since Nokia bought Trolltech, but now it's happened.
Qt, the cross platform library most widely used as the base for KDE can now be used by all projects, regardless of the license they use. Qt is an awesome library, and Trolltech was certainly justified in charging for commercial licenses, but it effectively nixed any non-open source activity on the KDE platform. If you just needed Qt for KDE support, the licensing fees were just too onerous to consider. (They stopped advertising them at some point, but IIRC they were about $4k per developer per year.)
This didn't nudge people to opening proprietary software, it just pushed them away from KDE to Gnome/GTK. Now that this hurdle is gone, both projects can compete on their merits rather than their licenses.