There are no restrictions on how much you can earn from a hobby activity. The difference between hobby activity and business activity is that hobby activity is not operating for gain. It is something you do in your leisure time and is not your main livelihood.
A hobby activity is normally taxed as earned income under the category employment income in the tax return. In principle, all income is taxable and all expenses are deductible. If you pursue business activity for gain, you must apply for F-tax and declare the profit under business income.
