I generally use bespin but lot of applications cant use it.
This qtcurve config was created to be used by gtk applications.
On screenshot you can compare bespin (dolphin) and qtcurve (easytag) with this style.
Import downloaded theme in qtcurve configuration window (window style) and apply it.
If you want to use bespin (if you do) just select bespin again.
In GTK+ Appearance must be selected qtcurve.