Oh Dear Lord
It looks like someone thought, "Hey, some people like Muine and some other people like Rhythmbox. Let's glue them together!". Please make it stop.
Update: apparently people think I'm mocking the author. Yeah, maybe a little. However, there are some serious cracky features in there, which I personally don't like, and as this is a personal blog this is where I get to say that sort of thing. Of course there is a hell of a lot of effort in this program (albeit in Python so its easier to get stuff working), but why is this another program?
We already have music players. If I only count the blessed and pratically-blessed players, there is Totem, Rhythmbox and Muine, all with different UI designs. The author of Listen must have at least partially liked one of those (from the screenshots he liked the playlist of Muine but the overall design of Rhythmbox) and then worked on one of those, say adding a pane to Rhythmbox to do what he wanted instead of duplicating large amounts of non-trivial code. It's likely that the result of this would look nothing like Listen, as I still firmly believe that it is ugly.
Of course what he does in his time is his choice and none of my business, so if he wants to write another music player he can, but if someone wants to make a real contribution to the community they should interact with the community in the first place. Otherwise it's just a pet project and if it duplicates existing programs, will likely remain a pet project. Maybe this comes down to centralised source code verses distributed source code (CVS vs Arch), but I doubt it. Downloading a tarball to start patching is easy, and for most people creating an Arch branch isn't exactly trivial.
Update 2: This is a very amusing open letter.