Comment 6 for bug 1278044

I'd think the easiest fix what the original one, Add a document and included in the .dmg file to tell users to:
  transferr to the HD,
 right click the app icon and choose open
 select open button

This only needs to be done once and no changes to gatekeeper need to be made! If user doesn't know about gatekeeper its better the settings be left alone.