@Ken Maltby: It doesn't. As I understand it, Kobo has *always* mounted the external SD read-only.
The issue simply lies in the fact that KOReader never tried to write in there before
.
We don't bundle luaposix, whose stat wrapper would have been perfect for this (AFAICT), so I had to resort to ugly hacks around io.open to check if we actually did have permission to do what we wanted. Hence the io.open calls, which will return nil if we can't do what we want (and/or if the file doesn't even exists).
So now, if we can't do it, we don't, instead of trying to no matter what, and wonderfully blowing up in subsequent calls because of a non-existant fd.
(I could also argue that, in both cases, dofile & insert are dumb for not handling nil properly themselves, but, hey, it's lua, it's designed to mirror ANSI C, so I can't really complain ;p).
[In case that wasn't obvious, I'm far from lua's biggest fan, so, err, take my comments with a grain of salt ^^]