Remote Buddy needs to change the Info.plist inside its application 
bundle (you can get there by opening the context menu in Finder over 
Remote Buddy.app, then select "Show Contents") at

Remote Buddy.app/Contents/Info.plist

This requires the copy of Remote Buddy.app you are using in a 
location Remote Buddy can write to. Usually /Applications should work 
just fine, but other locations, like your desktop, will work for 
this, too. Starting Remote Buddy from the distribution DMG file will 
not allow you to change this option, though, as it's read-only.

The error message will only turn up, if Remote Buddy can not 
overwrite the Info.plist file I previously mentioned.

Hope that helps.

Best regards, 
Felix