Yes, latest version of IM+ Talk application uses half-duplex mode.
We do not plan to change this currently.
All data is transferred via your internet connection (BIS/BES or wi-fi). There is no gateway number that application
uses to pass the call through. Your voice (call) plan is not used unless you use a callback feature of IM+ Talk application.
You may find more information at our FAQ:http://www.shape.ag/en/faq/sections/imskype.php