ported to OSX. not tested; almost definitely needs more work.

hey Mark,

rearchitected this to make it (hopefully) work cross-platform using the Automator to add a context menu entry and Cocoadialog in place of Gtk. not yet tested, but if you want to ensure I haven't broken it on Linux/Windows, that wouldn't be a bad idea... (I'll check myself later on).
I didn't, no, which is weird. I also committed a different fix for the error a few minutes ago that's more consistent with the way you had it working previously, but either way.