Developers need to get their games approved by Paradox and can only offer them through the Itch.io storefront. They can charge for their creations if they want, but they'll need to give Paradox a 33 percent cut of revenue.
It's neat to see a publisher and transmedia brand approve fan-made games. The fact that all of those six titles are in different genres is fascinating as well, since it shows the breadth of what developers can do when they have the freedom to be creative with a notable IP.