Stephan Binner of KDE fame has assembled a collection of distributor patches. Distributor patches are changes that different distributions make of the KDE sources to change the default behavior of KDE in some way.
For example Redhat would (for most of the Redhat 9.0+ versions) disable some functionality that KDE has that Gnome did not have because of a desire to see Gnome do better. Not all patches are for malicious reasons though. Many of the patches seem to be fixes to get specific compile time options working. Lindows has a patch to add text to kicker, thereby making it more “Windows like.” Overall there are some interesting modifications to KDE.