From now on I sell my themes to all countries. That is possible because I state sale taxes from this year on. Because of that, I am going to increase the price of Schlicht from 15 to 18 Euros on February 1, 2017 (circa the 19 percent sales tax in Germany).
Update from January 26, 2017: From now on, all customers can use automatic theme updates. Because of this, I deactivated the possibility to create an account on a purchase.
Besides that, it is now possible to buy a theme without creating a customer account. But if you use the guest checkout, this means you cannot use the automatic update process. You will need to download the new theme versions manually with a link you get after purchasing.