itch.io

Yes you can.  When you download the program there is a popup message that tells you explicitly that you can use them in commercial projects, but you can't distribute the art or spritesheets.  If I understand it correctly, you can't give the art away or charge money for the art, but you can generate spritesheets to use in a game that you sell.  Regardless you are good to use them in a commercial game project.