Hi, I am the creator of Photopea :) Photopea exists since 2013.
1. Nobody can buy Photopea, if I refuse to sell it.
2. I am not aware of using a work of someone else, or a unique idea of someone else. I would not be able to live in a world, where I am constantly scared, that someone more powerful can put me in jail, just because they have more money for lawyers. I hope our world is not like that, and if it is, I am ready to fight to change it.