Selenium isn't just the Python library you are using, it also has a separate piece of software, the Selenium server mentioned in your question, which interacts with the browser on your code's behalf.
This line of code
sel = selenium.selenium("localhost",4444,"*firefox", "http://www.google.com")
is trying to connect to the Selenium server in order that it can send commands to the browser (Firefox) as your code asks it to. "localhost" in the context of your script is one of ScraperWiki's servers which is not running the selenium server.
What you would need to do is download http://selenium.googlecode.com/files/selenium-server-standalone-2.28.0.jar and install it on a different server, running it with
java -jar selenium-server-standalone-2.28.0.jar
Then you could change your code to point to the server where you are running it. It gets more complicated because ScraperWiki restricts which ports you can connect out on to the internet with, so instead of using port 4444 you might need to use another one (probably port 80).
All told, I think it probably isn't a workable solution, you might be better off just writing your scraper in python, php or ruby.