Annard is correct in saying that you have permission errors that don’t allow DTPO to install scripts in the correct locations.
But running Disk Utility’s repair permissions routine isn’t the answer. The problem is an incorrect ownership/permissions setting of the Scripts folder at ~/Library/Scripts/.
In the Finder, go to that location. Select the Scripts folder and press Command-I to open the Info panel.
Near the bottom of the Info panel you will see information about Ownership/Permissions. Click on the Details triangle. Examine permissions. You should have read & write permissions. Change so that you do have read & write access to the Scripts folder, then close the Info panel and go back to DTPO.
Now select Help > Install Add-Ons. Confirm that you want to install the Add-Ons. That should do it.
If not, go back and see if the folders inside the Scripts folder also have bad Ownership/Permissions settings. If so, correct them to read & write and reinstall the Add-Ons.
For me, the issue wasn’t that the permissions themselves were wrong, but that the ownerships were wrong. For me, ~/Library/Scripts was owned by root, not by me, so I had to make sure that it, and all of its subfolders were owned by me, and now the add-ons install just fine!