So now I am trying to link up to one of my many external iphoto libraries.
When I try I get a caution message: “The iphoto library is locked, on a locked disc, or you do not have permission to make changes to it.”

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You can choose to get info on the hard drive.  It sounds like that drive may be formatted as FAT-32.  I'm not sure.  Just select to get info then choose to ignore ownership or permissions on that volume.  
You could also add yourself as an owner of that drive then grant yourself read and write access to the entire drive then apply the changes to enclosed items.