It looks like the developer(s) don't manage to keep up with courier's website changes and thus don't properly maintain it.
Some couriers changes are trivial to fix. The one that I use the most (OPT NC) only changed the tracking URL...
With open sourcing, the developer community would help with that. You'll still be able to sell the app. This app is really well-made, and I don't want it to die.
