(This is just my interpretation of the proletariat as a class and intellectual property, so take it with a grain of salt.) It's worth noting that in the post title's case, the labour embodied in YouTube as a platform and the advertisements shown by YouTube would have existed without the video creator in question. In Rowling's case, the vast majority of her wealth comes from her ownership of the IP, which is then "leased" by the corporations that produce the content in question (books, movies, plays, games, theme parks, merchandise, etc.), meaning that the source of her money is effectively rent. Since the IP isn't something tangible like a housing complex, I'm not sure if people like her are clearly bourgeois like landlords, but she's certainly not surviving by selling her labour power (so she's not proletarian) and she's not surviving by selling goods she created (so she's not an artisan)