Investigate a wordpress.COM solution
People running wordpress.org (self-hosted) instances could contribute by placing a badge on their site.
Wordpress.com bloggers, have restrictions like not being able to use JavaScript or embeds (like Flash, which is not required in this case).
However it's possible to embed something with shortcodes, youtube videos for instance.
http://en.support.wordpress.com/shortcodes/
They also provide widgets to place a calender (for example). Some of them use JavaScript.
There's a blank Widget (Text) for containing "Arbitrary text or HTML", but the iframe gets removed from it. (You also can not put JavaScript there on your own)
http://en.support.wordpress.com/topic/widgets-sidebars/
"Automattic" just have to allow this I guess.