What is the ruling on subscribing to the "YouGov Siraj" website, which relies on answering survey questions and accumulating points that are later converted into money, and is it permissible to invite others to subscribe to it in exchange for obtaining points?

If the advertisements are Islamically permissible, and the browser does not pay for browsing or subscribing to the site, and the advertising entity pays a sum of money when the number of points reaches a certain limit, then there is no harm in that. This transaction is similar to al-ja'alah (a reward for a specific task).