Looks like the API has changed, the build fails with several errors like the following:
examples-docs-moos/docs/examples/CommsExamples/EX40/ex40.cpp:70:8: error: ‘class MOOS::MOOSAsyncCommClient’ has no member named ‘AddMessageCallback’; did you mean ‘AddMessageCallBack’?
Comms.AddMessageCallback("callback_Y","Y",funcY,NULL);