While I love the David vs Goliath here, I'm going to point out the thing that open source folks just love to fluff over: Who is going to maintain that app over time? Maintenance sucks and is expensive. I'm going through this right now with a security system for a non-profit. The old system is open source and works--but it's 10 years dead. So, they'd like to add these couple features. Who is going to develop that? Who…
This is not a "current proprietary system" vs "open system maintained by volunteers". They can basically adopt the open system which is better and pay whoever they want the same account of money to maintain it. They just need to shift which system is being maintained. (And may even save money that way)