Fun read. You're a good friend.

I assume there was some additional context about the order in the form that the restaurant filled out, to assist in the end-of-month bookkeeping?

And unless you built reporting into the MVP, I bet your friend got to learn how to use some kind of database GUI (e.g. phpMyAdmin) and/or basic queries?

>The app would assign the order to a free courier, triggering an email. Their Gmail was our mobile app!

>The courier would then pick it up, deliver, take cash on delivery, and mark themselves as “free” again.

This tripped me up for a second. In this context, "free" indicates that the courier was available to pick up an order and make the delivery.