You cannot simply add properties to database keys and expect them to automagically have an effect in the templates. If you look at the template for the [printers] section for smb.conf, you'll notice a difference between how the "use client driver" parameter is set (with a variable) and how the "guest ok" parameter is set (with a fixed value). The last two lines before the closing bracket in the template expand to "use client driver = no" if the property "UseClientDriver" for the database key "smb" in /home/e-smith/db/configuration (that's what $smb{$UseClientDriver} means) is set to "no"; they expand to "use client driver = yes" if the property is set to "yes" or if the property is unset. In contrast to this variable line, the line "guest ok = no" is fixed in the template. The easiest way to set this parameter to "guest ok = yes" is to simply copy the file /etc/e-smith/templates/etc/smb.conf/50printers to /etc/e-smith/templates-custom/etc/smb.conf/ , then change the line "guest ok = no" to "guest ok = yes", expand template and restart samba.
{
$OUT = <<HERE;
[printers]
comment = All Printers
path = /var/spool/samba
browseable = no
guest ok = no
writable = no
printable = yes
HERE
$OUT .= "use client driver = ";
$OUT .= $smb{UseClientDriver} || "yes";
}