Hi LilFeffo,
When you buy Minifantasy packs, or acquire the commercial version of the free packs (Dungeon, Forgotten Plains and Creatures), you get a commercial license that allows you to use the assets on your game projects and release them on your platform of choice.
Check the license section at the bottom of the project pages of Minifantasy asset packs in Itch, or the license.txt that comes with all Minifantasy packs, for the license details.