I followed the earlier post but still have some issues first is syntax (no doubt a typo)
'codesign -vvv /Path/To/xbmc.app' is misleading, an example of the path would be so much more helpful. this worked for me
codesign -vvv '/Volumes/YourHardDriveName/Applications/xbmc.app'
next had to install Xcode. Latest version helped out a lot, but if using an older version we may need to apply a link
ln -s /usr/bin/codesign_allocate /Applications/Xcode.app/Contents/Developer/usr/bin/codesign_allocate
I believe this link applies to an older Xcode version, either way with it or the latest Xcode or even Xcode installed at all we may get an error "cannot find code object on disk"
Then this worked
Applied new certificate
codesign -f -s XBMC '/Volumes/YourHardDriveName/xbmc.app'
replacing existing signature
codesign -vvv '/Volumes/YourHardDriveName/xbmc.app'
valid on disk
satisfies it's designated requirement
Don't forget to remove and reinstall the firewall entry (like I just did) then YAY success
Thanks to all for this fix to a very frustrating issue