Hi, i was in trouble with this. When you have troubles about GPG keys in /var/log/zentyal.
After installing the vm i dont was able to update the components or install modules.
Here is a solution that works for me >
gpg --keyserver pgpkeys.mit.edu --recv-key 0E83F6EB10E239FF
gpg -a --export 0E83F6EB10E239F | sudo apt-key add -
It works, are keys suposed to Zentyal 2.0... in the Vmware version this works ok, but int the iso install image its not necesary.....
After this , i can continue updating the system and installing modules.