The following is taken from the OpenYMSG source project (http://sourceforge.net/projects/openymsg/):
"OpenYMSG is an open source Yahoo Messenger API implementation. It began as a fork of jYMSG, primarily to upgrade the API. It is intended to get you up and running with a simple Yahoo Messenger client in very little time."
Is there any reason SIP Communicator hasn't moved to OpenYMSG?