Specifically, it's boilerplate to prevent Firefox for being dinged for bog-standard browser behavior, presumably in jurisdictions where that might be a possibility.

Here's the clarification from Mozilla:

        We need a license to allow us to make some of the basic functionality of Firefox possible. Without it, we couldn’t use information typed into Firefox, for example. It does NOT give us ownership of your data or a right to use it for anything other than what is described in the Privacy Notice.

    The new policy merely allows Firefox to function as it always did, to help users visit web pages, allow the browser permission to store your personal information such as form data, or to access a file that you wanted to upload to a website.