First of all, I've noticed that net-firewall/firestarter-1.0.3 compiles fine but works only when net-firewall/iptables-1.3.5-r1 is compiled with extensions in USE. Second problem is that seting up an DHCP server with Firestarter creates a dhcp.conf file in /etc/dhcpd.conf instead of /etc/dhcp/dhcpd.conf. When I move the file to /etc/dhcp/dhcpd.conf I can then /etc/init.d/dhcp start and this works great.
[ebuild R ] net-firewall/iptables-1.3.5-r1 USE="-extensions -ipv6 -static" 0 kB Works fine here.