I have seen discussions of this sort of wording so many times over the years. My understanding is as follows (and I could be wrong, but this is my understanding of why that wording is used). If you use Firefox to upload a file to a website then, legally speaking,the browser is acting as a "publisher"of that file. Because of Draconian laws in many countries, to publish a file you have to have a legal right to the file, therefore Mozilla have to establish that if you use them to upload a file that you are granting them the legal right to publish that file. It has to be worldwide because you may be uploading to anywhere in the world.