I would say to register a company anyway and treat it as a way to charge for your work. You can use it for products and services too, if you want to sell any, but regardless of that it's a good mechanism that you will need anyway if you're into something big.

Note that this wouldn't work for a country where setting up a company would be a "heavy" operation so I can understan the author's advice in that setting. On the other hand, if it costs 50 euros or less and doesn't require much overhead if you have little or no activity, then why not.