Hi,
You can't use the script as a scripted graph. The easiest way to use the script is put it in your scripts folder (configured via File -> Preferences -> Application tab). Reload your scripts (Script -> Reload Scripts). Now you should have an entry in Scripts called batch-rendering. In the next release of Octane, the script will be always in the menu.
To clarify, there are 2 types of Lua scripts in Octane. Regular scripts and scripts that can be used by a scripted graph. Scripts for a scripted graph require a specific code structure. Those 2 types of scripts aren't interchangeable.
Unfortunately I don't have time right now to help out with the script. We're heads down in 3.0 development.
cheers,
Thomas