The playbuzz embed code has two parts - a script tag and a div tag. You can get it to load in Discourse by adding a site customization that appends the script tag to your forum’s head and then adds the div markup to the post that you want the quiz to appear in. This works, but it causes an error: Cannot read property 'offsetTop' of undefined. I’m guessing that’s related to Discourse infinite scrolling.
From looking at the Playbuzz forum - it’s a Discourse forum - probably the best way to do it would be to embed the quiz on a WordPress site with their WordPress plugin, and then embed an iframe on Discourse that has the WordPress page as it’s src. This works, but to get it setup correctly takes quite a lot of work.