If you would like to CHAT via the live stream you must have a Google/Gmail email account.  Once you open the live stream from the Calendar link, you will then need to log into YouTube with your gmail account in order to use the Live Stream CHAT feature.  Once you are logged into You Tube with your gmail account you will then be able to post a question/comment in the chat section of YouTube and the streaming moderator will read your question/comment on your behalf in the meeting.  Please be aware that there is a few second (10-15 second) delay in the streaming and chat, so the meeting may have changed topics (in real time) before your chat post would be read.