There isn't currently a full version of the program available for iOS. If they're referring to the app, we have a tutorial here that may be of use to them:
https://www.pgmusic.com/support.iphone.mac.htmThis app is intended to allow you open and play your existing songs that you've made from your Mac or Window's computer version of Band-in-a-Box. You can see what the limitations are in the link above. There are different limitations for Windows plus the app versus Mac plus the app, so at the top of the page make sure to click the link for the Mac or Windows version. I've linked the Mac + iPhone/iPad app link above seeing as we're in the Mac subforum.
The link that JayO submitted states in the app description as well which says the following::
"Band-in-a-Box for iPhone is a program that works as a client to your existing copy of Band-in-a-Box allowing you to play, generate and transfer your songs to/from your iPhone or iPad.
Important: You need to have the desktop version of Band-in-a-Box for Windows (2011 or higher) to be able to generate / edit songs directly from the iPhone/iPad. However you can download and play existing songs from any Windows or Mac computer."
Hopefully this clarifies!