Howdy! I started messing with Gift today and got Picklewickle running it. While he was doing his first run I found a way to get a key from a ghost without killing them (which can be seen in his submitted run he did shortly after I found it). This works on v03 at least, haven't tested earlier versions.
While standing on the edge of the screen as a ghost holding a key approaches, wait for the ghost to be nearly on top of you so that the key sticks out past the edge of the room. Screen transition at this point and the key will be laying on the ground next to you.
You can pick it up and use it as if you'd killed the ghost normally to acquire it. If you don't pick it up and re-enter the room the ghost will have it again; this doesn't allow for key duping afaik so I don't think there's any value to it yet.
there are many uses for this, it's basically always faster than taking the time to kill the ghosts, at least in my timing!