LineBorder2 installation

You didn't have to install Python package for GIMP 2.8, it's already included in standard installation.
Just unpack LineBorder2 in your Profile plugin folder, download glade from this node http://registry.gimp.org/node/24503 (the last entry in Attachments) and copy files to corresponding folders in your GIMP Program directory. Last thing to do - go Edit/Preferences/Folders/plugins and add path to LineBorder2 subfolder(s). Restart GIMP.