We just released an update that allows you to use https for Facebook apps that use sitebox.
Facebook recently introduced the setting for its users to always browse it securely using https. This doesn't automatically extend to Facebook apps, since each app needs to work through https. And if you're using Player.IO and SiteBox, your app now supports it.
If you have an existing app, the only thing you need to do is to enter the Secure Canvas Url. You can find it in the setup guide in the admin panel here, and you need to enter it on the Facebook Integration tab of the app settings on Facebook. You also need to ensure any hard-coded URLs use the proper protocols, for example external javascript libraries. Any assets that you add through the {% url %} template tag will automatically work, as well as relative links.
If you make a new app, the example game will just work by default.