Ham from mapgea - a OpenData IOS app that connects citizens with their cities.
For public decision-making algorithms, I have a strong preference on open source solutions, as transparency is paramount here.
If it’s more of a communication layer (such as visualization and presentation), then proprietary solutions surely has its place.
However, the data exported by such systems is still better released with an open license, and the APIs it takes are still better documented in a machine-readable format; there two can define a much more composable interface between various sectors in the society.