It can be REAL! After the sufficient, but instable, KDE3 compiled on Mac OSX, seems that KDE4's developers are working to run it on Mac OS X.
From Tales of Racoon Fink:
So I've finally gotten things pretty much set up for autobuilding KDE4/Mac packages. Universal packages for 10.4 are available here and I'm working on getting 10.3 packages put together as well. I'm still setting off the build process manually for now so I can watch it, but assuming things work out, they should start updating nightly sometime in the next few days. (Well... Assuming everything builds, of course.) ...