You can enter the chatroom without registration by entering a nickname and using the chat button. If you want to use your webcam/mic for the chat you have to create an account with stickam.com first and use that when entering the chatroom.
You can ask the speaker questions using the Stickam chat, or in the #sfpug channel on irc.freenode.net.
The "Operator Exclusion Constratints" talk is scheduled to start on Tuesday, December 8, 2009, 7:15pm Pacific Time (or 2009-12-09 03:15:00 UTC).
Streaming video brought to you by Dirk Jagdmann and Chanticleer Films