When you own a website that sells digital goods, is it considered as being self employed?
Yes. In the UK, if you’re making money then you need to register for self-employment.
Selling online requires that you get a business license and register an account with your state for tax collection.
You can’t just start taking money in exchange for product.
You can. You just need to register for self-employment (for tax reasons like you say). It depends on where you live though.
So I have to get a permit if I open a website. Working on it…
here in the US of A
you ? can? but!!!
you will have tax issues if the proper filings are not filed and if you are NOT incorporated then you could loose your house or car or owe $10,000,000 + if you are sued
not sure in the uk or eu but here forming a limited corp is very easy
I live somewhere in Asia by the way.
So, the only way that you can get a useful answer to your question is to contact (ugh) a Lawyer … in Asia. Specifically in your home town. In any part of the world where bureaucrats exist 
there will be paperwork and tax-reporting.
It comes down to locale laws for things like income-tax. Here in the states if you make more then a specific amount then you have to pay a % of it at the end of the tax year.