In most EU countries law, this one is also considered as "solid business", regardless if you are incorporated or not:
If you are running on a level with focus one some revenue, if you are doing it somehow regularly and if you have at least some infrastructure to look like you are a corporate (billing system, customer care or similar), then you may fall under corp rules, even if you are not acting as an entity.
But as with anything here in Europe, check your laws.