Apache Wave (I believe the intial code was contributed by Google): http://incubator.apache.org/wave/source-code.html http://incubator.apache.org/wave/source-cod

Apache Wave (I believe the intial code was contributed by Google): http://incubator.apache.org/wave/source-code.html http://incubator.apache.org/wave/source-code.html I don't think it has gained much traction, though.