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I am sure what you are looking for, but the purpose of the extension is not to open the website
This is literary explained in the OP
What is this?
A web browser extension ("add-on" in Mozilla-speak) that provides additional features to BitcoinTalk.org. Some of these features use data from BPIP.org, some others work entirely inside your browser. The extension activates when you browse BitcoinTalk.org pages such as threads or user profiles and inserts additional info about BitcoinTalk users and additional controls.
When you click on the extension, a configuration page appears, which is normal and lets you configure it to your best preference.
The domain name bpip.org is so easy to recall, so I am not sure why you need an extension in order to open it.