Typescript compiles down to ES5, so yes you can write in ES5 but it's not as pretty. You can create a class the standard way using `prototype` and from memory the annotations look something like this:

    MyComponent.annotations = [
      new angular.Component({
        selector: 'my-component'
      }),
      new angular.View({
        template: '<div></div>'
      })
    ];

No, you don't have to use TypeScript, the angular dev team has been clear on this. You don't have to use atscript either. That said, typescript is pretty slick, and is essentially ES6+, I'd recommend giving it a shot before dismissing it.