The planned xAP MainLobby plugin is on hold. This is because it has not been possible to reach a satisfactory agreement with Cinemar. They do not seem to believe in 'free' plugins and regard xAP as somewhat competitive to Cinemars' own plugins. The fact that it is so easy to add devices to MainLobby using a xAP plugin seems to be a worry as it detracts from future income opportunities for them. As Cinemar control the availability of plugins via their licensing system it would not seem worthwhile pursuing a xAP plugin at this time.
Currently you can integrate MainLobby with HomeSeer very nicely using the mlhsplugin and because HomeSeer has several xAP plugins available this is the recommended route to achieve xAP integration in MainLobby.