They confirmed here: http://groups.google.com/group/google-wave-api/msg/b6649dcc5...
"Yes! The plan is to release a reference implementation of the client, as well as the server. "
"Yes! The plan is to release a reference implementation of the client, as well as the server. "
And yep, some people can't wait so here is a server implementation (Python/Django):
http://code.google.com/p/pygowave-server/