*****YES, YOU CAN USE DROPBOX IN KDE WITHOUT A KDE CLIENT!!!*****
The filemanager integration (the nautilus-only part) is for putting the little status icons on dropbox files and allowing you to copy the public link, etc. The Dropbox daemon dropboxd is what interfaces with Dropbox the website, and keeps the folders synced; and it is not dependent on nautilus, Gnome, KDE, Dolphin, Konqueror, or anything of the sort. It will work regardless of your DE or FM.
So what do you need to do? Well, it’s quite simple. 🙂 Download the daemon from http://www.getdropbox.com/download?plat=lnx.x86 (x86_64 for 64-bit), and extract it to your home directory. It made a hidden folder called .dropbox-dist. Now run ~/.dropbox-dist/dropboxd and that will help you setup your Dropbox account and provide a tray applet (works in KDE, don’t worry) that kindly tells you when it has synced your dropbox folder. That’s it!
Sorry if this is already in an FAQ, KB, or forum post elsewhere. I couldn’t find it, and I wanted to make life easy for my fellow KDE-ers searching for a Dropbox client.