Of course, being free software people can pretty much choose what they want to work on and when. KDE core development is based on contribution from a large group of free software developers. This is excluding the hundreds of applications not maintained in the KDE CVS and part the KDE project itself. Once that is done you can work either in our CVS or via patches. The core packages are largely a collaborative effort and gets the attention of a large group of developers.
Individual packages are usually the efforts of either individuals or small groups of people.
As an application developer, the approach you take is largely a matter of style. Most notably Linux Mandrake, Suse, Caldera, Corel, Red Hat, and Troll Tech all have developers dedicated to KDE - and that's just what comes to mind. There are also several non-Linux distribution companies I know of that are acquiring KDE developers for free software development. The difference between KDE and competing projects is KDE developer funding seems to be spread over a wider group of Linux companies. You don't have one or two interests controlling an important group of KDE developers.