Pretty sure it's Apple Menlo, which IIRC from my OS X experience is the default font for Terminal.app. (Or is it? Might have been Monaco. I'm sure it's one of the two, and the other is the one I ended up preferring for reasons I've since forgotten; they are very similar overall.)
Monaco is a vectorization of a bitmap font that dates back to the original Mac OS (possibly even older). Menlo is an entirely separate font -- it's a version of Lucida Sans Mono with some minor tweaks by Apple.
This one is clearly Menlo. Monaco had some peculiar letterforms, including an odd "asymmetric" loop in lowercase letters like "b", "g", and "p". The LSM / Monaco shapes for those letters are much rounder, and that's what I see in that image.
