To add context to Intenselog's comment. Websites featuring adult content are required to ask if you're 18 or older. Itchio however does not. Requiring the app be purchased acts as a pseudo-age verification. In the event they get sued they only need to bring up the receipt to show they did their due diligence. The reason it is 5 USD is due to free trial exploits. Most banks and whatnot use a hold charge method that typically ranges between .99 USD and similar. By making it 5 USD they can bypass anyone using these exploits. They were fairly common in the early 2000s to access trial based membership adult websites. They have yet to be patched.