The Beta version of Google Chrome 6 was released on August 11, 2010. The browser has several versions as you can read in the post: Google Chrome – Software channel breakdown, since that post was written, Google even created a new version named Canary but that is a topic for another post.
Chrome uses the source code of an open source project named Chrominum. The project is in version 7 at the moment.
At the time this article was written Google Chrome stable version is 5.0.375.127.