The message you are seeing from qdbus is because kded4 is not running / has failed to start. As it launches fine when you run it by hand, we need the log output from launchd in order to diagnose why it fails to launch in this environment.

Again, the issue is not with launchd, it's with how it's being used. So launchd never notices that the "framework" it launches fails (or is simply not designed) to start kded4. That's what makes it a MacPorts issue, IMHO.

The problem isn't with launchd. However to find out what problem kded4 has with being launched by launchd, we need the output of kded4 - as launched by launchd. This should be contained in a log file of some description kept by launchd.