It’s not open source, but it is developed by a reputable indie team — I recognize some of the apps they’ve made (though Access is new to me!).
Especially for a high stakes app like this, I think it helps to know who develops it. So, for reference, here are links to the developers X accounts’:
Now—to be clear—I’m not recommending this app as I’ve never used it, but I thought it might help to provide this extra context.