i do believe you can. Winterboard lets you use a Widget.html file and will run it normally. I do believe though that particular .html file is not working. That is why a lot of people have to use wallpaper grounds in their widgets. They are being written as wallpaper.html files since Widget.html files isnt working right now..
of course, i'm just guessing as i'm not a dev. Just quoating on my personal experience….