There is much discussion in this document about securing and restricting the contents of the directories, from $KDEHOME to $KDEDIR and $KDEDIRS. Here is a description of what these contents actually are.
This section is heavily based on Richard Moore's article at http://developer.kde.org/documentation/standards/kde/fsstnd.html. If you intend developing software, there is help there on how to use the information that follows.
Directories look like this: directory/
Where you see appname it means that there should be an entry corresponding to every installed KDE application.
Where you see lang, it indicates there should be an entry corresponding to every installed KDE translation.
bin/
etc/
lib/
appname/
kde2
TODO: Get a really good explanation of what this is for and why!
include/
kparts/
TODO: ASk about this.
kio
TODO: And this one.
man/
TODO: When we start installing our own man files, will they be also stored here? It seems the obvious thing, best to check though.
parts/
TODO: Is this still correct? I've never seen or heard of such a thing: parts/
share/
aclocal/
applnk
apps/
autostart/
config/
doc/
default/
lang/
appname/
icons/
locale/
mimelnk/
services/
servicetypes/
sounds/
templates/
wallpapers/