This website is under GNU General Public License v3. The repository is open-sourced on GitHub. Frequently Asked Questions about the GNU Licenses can be found at https://www.gnu.org/licenses/gpl-faq.html
Some assets you found on this website didn't created by myself. I know that making good things like that takes a lot of time and effort, so I proudly to give them an attribution to credit the creator. Because this website has a pixel vibes, I convert them to a pixel first using Pixel It—if they are not pixel arts by default.