I've been exploring the idea of building a food delivery/logistics solution for myself as well. I've looked at Saas based options and I am really turned off by not having full control and basically just "renting" the solution from someone else.
I've tried searching for alternatives but it mostly leads me back down to the Saas hole.
Can you tell me how you found out about the solution you're working with?
Also, how exactly is it open source?