Host software check, zenity possible failure
See line 240 of script. Do not check if a software is present by querying a package manager that's not supposed to be installed on every possible host that can run this script. Check if exists in /bin, /usr/bin or whatever distros is supposed to keep files after checking it alias already exists for the current shell.
I don't have zenity installed but I doubt it works when X server is not running so don't even bother calling it like that: it will probably fail for those using (local|remote) consoles like system administrators.
Showing text should be done by checking following programs availability in this order: zenity, dialog, whiptail, less, more.