Note to myself:
If you ever try to uninstall IBM Lotus Sametime Gateway and the uninstaller always tells you that there are still running processes / servers and therefore no uninstall is possible even if you have made sure that all services, processes etc. are stopped:
Have a look in your Websphere profile log directories (<WAS_install\profiles\<profile name>\logs) and delete all *.pid files which still might exist there. Afterwards the uninstall should be possible without problems 😉