yes, the api key is optional, the first page of the pro maps wizard has a few paragraphs above the API key input field field that talk about the api key being optional and how to obtain one.
When i visit the link you provide, the map appears to be working for me, see the attached screen shot.
![](/forums/attachments/135345/cache/var/www/vhosts/webassist.com/user_uploads/forums/attachments/135345/proportion/Screen%20shot%202012-08-21%20at%201.04.14%20PM_w138_h100/Screen%20shot%202012-08-21%20at%201.04.14%20PM_11170736.jpg)