Never made a flat version of it, since it was only required for the app website and icon for the iPhone, and Droid. Although if I did, it would either just be the plum by itself, or a cut-out outline between the plum and the pin to separate the two.
A logo is indeed an icon in the most basic sense of the word and vice-versa: they're both symbols used to represent a larger idea. But both have their respective requirements and purposes. A logo is something that is intended to be massively versatile, and should be reproducible in many many formats, sizes, colors, and applications. An icon is more appropriate for a piece of software that sits in a dock, though, because in this instance it has a more limited application range (mostly just on-screen, rarely smaller than 16x16, but typically a minimum of 32x32) and people expect icons of this sort to be more rendered and visually "pretty."
This is why I said it's an icon instead of a logo. It wasn't out of quality (which, it's quite nice) but more out of intent.