Is there a "reverse" Musescore?

from midi to a score? MuseScore! Excuse the joke, try to search here: http://www.hitsquad.com/

Realistically, the process of "understanding" a recording in this way is beyond current technology except in the very simplest of case. That is, a recording of a single instrument playing one note at a time - that's doable. Taking a pop song or symphony and sorting out all the different instruments involved and which is doing what when? Not likely any time soon. There are indeed products on the market that can try to deal with the easier cases - do a searhc for "pitch to midi" or "audio to midi".

For polyphony, I stumbled upon this years ago:
http://www.pluto.dti.ne.jp/~araki/amazingmidi/
(I still had this link in my 'favorites' folder, though I have never tried the app.)
There is an interesting musical conversion example on that website.

Supposedly, it outputs a midi file from a .wav recording of a single instrument - even a polyphonic instrument. The midi can then be imported into MuseScore.

The program claims to recognize the tone color (timbre) of the instrument from a (user created) tone file, and then writes down all detected .wav notes as a single instrument midi file.

There are some tools in the professional mastering area which are able to isolate single events. For monophonic voices there were some functions in common sequencers, but nothing a trained ear could'nt do better. If you're satisfied with harmonic Analysis, band-in-a-box (pg music) makes good guesses on chords, also transscribe (7th string) does some spectral analysis to Support guessing.
Last not least most copyrighted material is sooner or later marketed as scores anyway, which is by far the most proper way. Ok, most often These scores are oversimplified, the Prices the author's share and bundling with stuff you don't want is worth a discussion but that wasn't he question here.