The tool should be open-source. I am a huge believer in open-source. That does not mean that everything that we use should be open-source. There is a time and place when we should use enterprise editions of the software, and there is a time and place when we should use a service. However, in this case, I wanted to make sure that it is free that it is open. So, open-source is a requirement, at least for this course.