Can't launch application as root: secinitd > registration request failed
Found a solution myself:

sudo /bin/launchctl asuser 0 /Applications/Calculator.app/Contents/MacOS/Calculator

Console:

26/08/16 15:12:25,946 sudo[34364]:    USER : TTY=ttys000 ; PWD=/Users/USER ; USER=root ; COMMAND=/bin/launchctl asuser 0 /Applications/Calculator.app/Contents/MacOS/Calculator

26/08/16 15:12:27,891 secinitd[34367]: UID[0]: cache loaded: /System/Library/Caches/com.apple.app-sandbox-cache.plist

This will ensure that the request actually comes from 0, not from 501. It might not be the only possible solution, but it worked here. If you know any alternate methods, let us know. Thank you.