gettext is more of a pain than you'd think unless you're in C or a C-with-a-hat-on-it like PHP. As I mentioned elsewhere in this thread I settled on Excel XML files because gettext (which I of course looked at first) wasn't a worthwhile format for either Java or .NET. And given that Papers Please is (I think) written in HaXe, I don't know what the story for gettext support is there.

That's without getting into licensing headaches, which is why the idea of P/Invoking GNU gettext is a straight-up nopenopenope.