Well not many creators make money on Itch.io anymore (you can thank Visa/Mastercard for that)
You will notice links to Patreon, SubscribeStar and Steam on here, this is where the revenue comes from, think of Itch as a try before you buy system. Like Wikipedia it is free to use, but they will ask you to make a donations where you can.
For Kal, this is a little different with Starmaker and not sure how much I should say. Basically one of their projects did not workout, Starmaker is kina like a makeup project, to help the developer get back on form and something to play while we wait for Roundscape Eclipse. The game will always be free, but you are more than welcome to make donations via Patreon & SubscribeStar and purchase the game on Steam when it is complete (this will be including an exclusive character, quest and some additional costumes for Anna in the Studio) Though any money made really goes towards Roundscape Eclipse, which is the main project and focus for Arvus Games
To put it simply, nobody is rich far from it, this is pure passion and coffee and the hope is people will throw a coin in the hat every time the monkey dances...