In AS12.1 Branch the debug log is being created by creating a file called debug.txt in Z-Push Folder (this I did not change - please search the forum what exactly needs to be done).
The Username => Fullname mapping does exactly work how it is being defined... You login to Z-Push Server by using a username. This username is during send/reply/forward being matched against this list and in case a full name is being defined in the list it is being used in the email that should be send.
Using Zarafa 7.0.7b1 with my tuning patches, Z-Push AS12.1 Branch with GZip, SMS, SMime and HTML Support. Patches are available upon request and being announced on #IRC.