This post is a bit late but may be relevant to someone.
I run a small LAN with a Zeroshell Release 1.0.beta12 routing SIP traffic to a Asterisk VOIP server via virtual server rules. It works very well for us, However I have not been able to update to Release 1.0.beta14. When I load beta14 I find that the incoming audio traffic on port range 10000-10100 gets dropped. I used TCPDUMP on both the beta12 and beta14 builds to confirm this but have not been able to work out why it happens.
And as for VOIP server recommendations, I spent quite a bit of time looking at alternatives to Asterisk and have concluded that Freeswitch with a FreePBX UI would be an optimal solution. I have trailed this on a test server and it works well and is easy to install and maintain on Debian.
I have just been looking into this and found a reference to dynamic DNS support on the dNSZone home page (I believe ZeroShell uses dNSZone as the LDAP back-end for BIND 9):
A number of people have asked for Dynamic DNS support, or how they can make their DHCP server do DNS updates. There is now a tool that allows a zone to be updated based on the ISC DHCP server’s lease database updates. The tool is dhcp2ldapd-1.1 and is a Perl script written by Travis Groth.
I would find it very useful. Would it be possible to add this to ZeroShell?