After rebuilding my personal website last month, I switched over to serving it over https. This had the unfortunate side effect of preventing me from embed Sketchpad sketches on my website, since the embedded iframe wasn't also served over https. This was enough motivation to make some changes. As of today, the "embed" code included in the footer of any canvas of a sketch created in the public studio at studio.sketchpad.cc or created anonymously at sketchpad.cc can be embedded in a web page served over https (like this one!)
If you'd like to try embedding a sketch on your own site, here's a cool game written by Mitch Davis to use as you practice. Hover your mouse over the canvas footer and click on the "embed" link. Copy and paste the embed code into your own webpage and try out the game!