After upgrading my Mac to OS X Yosemite (10.10) I had to reinstall Java to make IBM Notes startup just like Rene describes. To install go to the download page for Java on apple.com, download and install. It takes around 5 minutes and you are ready to go. Once installed the Java runtime makes IBM Notes fly again and I can confirm that the OnTime Group Calendar UI’s run just fine on OS X Yosemite.