Well there is your issue. This importer is written to import coppermine to photopost standalone to standalone. bridges are gonna cause things to be out of whack.
Example if your coppermine does not have users in it where are we going to grab the user from? see what I mean?
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we look at your coppermine photos table to see what the owner stuff is. If your users do not exist in coppermine then you can run into a serious issue then. If the users username is still there maybe you can use this script to get the right userid
That will work for any forum