I also tried to make the game linux native compatible but you have this thing that sets where the save files are supposed to be stored that I don't know how to fix because I don't get it. In Linux it tries to do it in the root directory (equivalent to C:/) which is a place no one besides the admin has access to so it gets an access denied error
var path = window.location.pathname.replace(/(\/www|)\/[^\/]*$/, '/save/');
You are probably not interested in making it linux native but I say this in case someone else is.