I've just got hello world working with the KDE4 version of the ruby korundum bindings. Here's what it looks like:
require 'korundum4'
aboutData = KDE::AboutData.new( "tutorial1", "Tutorial 1",
"1.0", "KMessageBox popup",
KDE::AboutData::License_GPL, "(c) 2006" )
KDE::CmdLineArgs.init(ARGV, aboutData)
app = KDE::Application.new
guiItem = KDE::GuiItem.new( "Hello", "",
"this is a tooltip",
"this is a whatsthis" )
KDE::MessageBox.questionYesNo( nil, "Hello World",
"Hello", guiItem )
I got it from the KDE Developer's wiki here. That example doesn't have the new KComponentData class that used to be KInstance, and so I'm not sure if you're supposed to pass 'aboutData' to both the KDE::Application constructor and the KDE::CmdLineArgs.init() method as above. Note that you need to require 'korundum4', so it will be possible to run the KDE3 version of Korundum at the same time