The file /Applications/The Darkside Detective 2.app/Contents/MacOS/The Darkside Detective 2 is missing the executable bit when extracted, thus the game can not be started. Opening Terminal.app and executing "chmod +x /Applications/The\ Darkside\ Detective\ 2.app/Contents/MacOS/The\ Darkside\ Detective\ 2" fixes this issue.

Thanks for the note! I'll flag this to our developers so that we can hopefully log and address any concerns going forward!