KDE on Mac OS X has a long history, but is seeing new life in KDE4 and Qt4/Mac by bringing native KDE4 applications to the Mac OS X desktop.
If you are interested in installing KDE 3.x on Mac OS X, check out the KDE 3 page.
KDE 4.x on Mac OS X is quickly reaching a stable stage, and currently could be considered a "technology preview". Official support for Mac OS X is targeted for KDE 4.1.0.
Mac OS X is already a "desktop environment" in the sense that it provides window management, application launching, etc. The goal of KDE on Mac OS X is to provide the rich frameworks and applications in KDE to a wider audience.
In KDE 4, we intend to have:
Perhaps not all of these things will be available by 4.1, but the goal is to do as much as possible for release.
You must install at least Qt, kdesupport, and kdelibs for any of these packages to work. Note that kdelibs requires soprano and strigi. Also, kdepimlibs and kdebase are recommended since a number of things will want them. (...and it has Konqueror)
The instructions listed for installing amarok from source can be adapted to install other KDE4 programs from source. See http://amarok.kde.org/wiki/Amarok2_On_OS_X for details.
See the official KDE/Mac web page for download details.
If you want to compile against these snapshots, you also need cmake. You can get the latest release from their download page.
Running apps should usually work from Finder. But if for some reason they don't, you can try these two steps:
From the command line, update PATH and launch dbus, like so:
export PATH="/opt/kde4/bin:/opt/kde4-deps/bin:/opt/qt4/bin:$PATH" eval `dbus-launch --auto-syntax`
Then, to start an app, you call it from the same terminal, like this:
NOTE: Don't try to start the 'real' binary directly, like so:
since this will result in various interactions with the OS (drag and drop, for example) not working.
Sometimes, Installer.app fails to run the post-install. Try running:
...and see if your application starts.
If you'd like to try building KDE yourself, it should (mostly) work out of the box. You can get tips on building here (including a link to the tools I use to generate these packages).
There's still a lot to do. I'm going to try to keep a running list of what needs to be done on the TODO page.
You can find the KDE4/Mac developers in the #kde-mac IRC channel on FreeNode and folks working on KDE4 in general in the #kde-devel channel. This should be the first place you look. If you have a question, be patient, sometimes we're logged in but not looking at IRC all the time. If you stick around, we'll answer.
The official list for KDE/Mac development is firstname.lastname@example.org.
There are lots of great mailing lists for more general KDE discussion. For a complete list, see the KDE mailing list page. The KDE/Mac developers have been known to hang out on kde-buildsystem, kde-devel, and kde-nonlinux.
First of all, before doing anything else, check the KDE bug page to see if your problem has already been reported. If so, add as much as you can to the existing bug report to make it easier for developers to figure out what's gone wrong.
You might also want to try the IRC channel(s) before filing a bug, you're more likely to get a quick response there. Also be aware, we know there's still stuff broken on Mac OS X, so be gentle. :)