The demo appliance is in playback mode and contains custom pattern, etc for the demo.  Please see discussion in http://discovery.bmc.com/community/forum/viewthread/2546/

Seems like Community Edition is a sort of trial version if I understand this correctly: BMC Atrium Discovery Community | ADDM 10 | The Community Edition

The Demo Edition is loaded with already discovered data from BMC that you can use to learn how the system works. It is also per default set to playback mode, you cant perform live scans when in this mode.