Norah, not really. It’s self-employed income, rather than PAYE, hence being taxable after expenses, but still income. What complicates matters somewhat in this case is that it’s income earned in multiple tax jurisdictions. Although, if Harry’s tax country is the USA, I believe they have a flat 30% tax withholding on foreign income. He’ll have good accountants, and under the American tax system, he can claim back the cost of them as expenses!
Are you sure your brother pays tax in both countries? It’s possible, but more common (and annoying) to have to file (do a tax return) for both countries, but not to earn enough for double taxation.