“Downloading from LimeWire. You're not paying, but you're not taking anything tangible. Is this kosher?”
Technical note - LimeWire is a "P2P" or peer-to-peer networking service, in which users upload anything - movies, music, games, software - and can be downloaded, for free, by virtually anyone.
In my experience whenever I hold a Q&A session with a group of teens or college students, the question of downloading music, etc., is one of the first questions that will be raised. Moreover, even boys and men who in other issues are meticulous in their quest to act lifnim me'shuras ha'din (beyond the letter of the law), when it comes to this issue, they very much want to know the minimalist Halachic position – i.e., how much they can “get away with” and still technically be within the bounds of Jewish law.
Accordingly, let me begin by stating that from an ethical perspective, it behooves a Be en Torah who aspires to rise above mere technical compliance with Halacha, to refrain from any form of downloading which is questionable. Most of us – although we may deny this when we are in rationalization mode – know very well when what we are doing falls into that gray area. If you are still unsure as to the definition of this category, by all means consult one of your Rabbeim.
Returning, however, to the question of the minimalist Halachic position in this area, Rabbi Yitzchak Yosef shlita (the son of Rabbi Ovadia Yosef shlita) refers to the Gemara in Bava Metzia (24a-b) that discusses an object that was swept away by a tidal wave (zuto shel yam). In that case, we regard the object as a lot item whose owner has given up all hope of retrieval (l'achar yei'ush). This is the case even if the owner watching the tidal wave sweep away his possession declares and affirms that he is not giving up the hope of retrieving his object. Under the circumstances, his declaration is meaningless, as the hope of retrieval is regarded as little more than a fantasy.
Any music that is freely and widely available on the web falls into this category. Any hope that the owner may have of retaining or retrieving his intellectual property is futile and meaningless. Hence, one would be permitted to download such music for personal use.
Please note that this is not carte blanche. This logic will not permit:
Uploading music to such sites.
Copying from CDs or DVDs.
Selling the downloaded music to others or sharing it with people who cannot access it themselves over the Internet.
Downloading music from hacking sites.