You don't have to. As long as you're logged in to the account you've used to purchase it!
4 years ago(+1)
When I go to this post about the bugs been fixed, it says buy it. This is something I don't understand.
4 years ago(+1)
That would be itch.io attaching it to the post. You can re-download it by going to the main page and it should show this button.
It should lead to the download page like the one below.
Hope this helps!