If you mean Wave, there is some code open sourced (syncronizer), and we're working on getting the rest out. Also, we have federation testing. You should join the dev list if you want to try it out. There are some neat non-google implemented wave servers based on the protocol docs we released earlier this year.

not the servers, the code that produces the web app I see at wave.google.com

Actually, we intend to opensource the UI as well. So server + federation + syncronization + client ui.

As remember from the early videos there is a limited client without some of the features (statistical spell checking) that is (or will be) available open-source.

By client you mean the browser you run to use Google wave?

Are you saying that gmail is "open source" then? hotmail? I think they are probably talking about the code your browser is executing.

Still not sure what he is referring as the client, the wave interface?

Yes, the Wave interface. The Wave interface acts as a client of the Wave protocol and servers they have running internally, hence his use of the word "client".

the code that produces and runs the web page that I see when I go to wave.google.com