Christian,
did you already take a look at Coccinella?
"Coccinella is a free and open-source cross-platform chat client with a built-in whiteboard"
(from
http://hem.fyristorg.com/matben/)
Following Caroline tips maybe you could take a look at Coccinella as possiblity to integrate dotlrn with an external service based on XMPP protocol. A time ago Malte and others elaborate a to-do to get XMPP support for OpenACS and one of the biggest goal would be to record Coccinella whiteboard messages. The original forum thread is here
https://openacs.org/forums/message-view?message_id=189152
Please keep us informed about your ideas.
