This is kinda a tough question to answer.

Is it free? Yes, this is not some musicdownloading site, Limewire just connects you to other people using similar apps. It gives you access to the files they share and vice versa.

Depending on which country you live in this can be legal or illegal. Also when downloading Limewire you had to check a box, that said that you would not be breaking the laws regarding copyright, before being able to download it. (Unless you got it from a scamsite claiming legal music downloads blah blah blah, and ripping you of in the process).

Some people respect copyright and others don't. If it's illegal in your country to download/share then various organisations could come after you demanding payment for what you "stole".

Most people still buy the occational CD even if they can get music of the internet for free. Especially small labels are hurt if noone buys one of their albums, and if you like something, then why not support it, so you might get future releases from those same bands.

Like a try before you buy kinda deal.

Hope this gave you some idea of how complex this is.

For more info use the forum search. Look for legal , illegal , copyright , riaa , mpaa , recording , industry , and many other. You can use like e.g. copyright+illegal etc when you search to get the most relevant results