One significant advantage that Selenium seems to have is that it accepts CSS3 selectors as target element patterns. Chickenfoot has XPath, but not CSS3. A bit of a bummer because this otherwise looks like it will be fun to play with.
Regarding Google, you might be thinking of the on-going merger between the Selenium and the WebDriver projects. WebDriver was created by Googler Simon Stewart. He currently works at Google, but WebDriver was created when Simon was still at ThoughtWorks. Also, I am a former Googler (and former ThoughtWorker), and worked on Selenium during my time at both places.