The process described here sets up a MacPorts installation of the latest stable KDE SC release and uses this to then build a KDE trunk development environment. This approach has the big advantage of using MacPorts to build, install and keep updated the base system and libraries required with minimal effort and without touching the base OSX system install, and allows you to run stable KDE apps for everyday use while still developing on the unstable trunk.
The big disadvantage is compiling all the MacPort dependencies takes longer than binary installs.
This process makes use of David Faure's scripts.
Install XCode and X11.
Install Apple's XCode developer tools either from your OS X install disks or download from http://developer.apple.com/technologies/xcode.html.
If you are running Tiger you will also need to install Apple's X11 from your OS X Install disks. Snow Leopard and Leopard come with it installed by default.
Once installed, perform an OS X Software Update to ensure your system is fully up-to-date and reboot if required.
"The MacPorts Project http://www.macports.org/ is an open-source community initiative to design an easy-to-use system for compiling, installing, and upgrading either command-line, X11 or Aqua based open-source software on the Mac OS X operating system."
It is recommended to initially install MacPorts using the package installer as this will automatically set-up your required $PATH.