JSONObject (& JSONArray) should not be final, to allow json-based type safety that interacts well with Tapestry

For example, one might want to make a special type to communicate with the client-side page:

class AlertMessage extends JSONObject
{
    AlertMessage() { put("type", "alert"); }

    public void withMessage(String message)
    {
        put("message", message);
    }
}

...such would minimize the proliferation of the field name strings, allow passing custom json-backed types to various pages & services, etc.