Oh, you have three of them, even better!
Plan 9 is free:
http://plan9.bell-labs.com/plan9/
Somewhat primitive but fun.
eComStation is available on a Live-CD to try.
http://www.ecomstation.com/
I took PC-BSD for a spin just a week ago, it's a FreeBSD-based polished desktop system with KDE. Very nice if you've seen the horror that is NetBSD and/or OpenBSD-installation.
http://www.pcbsd.org/
And it doesn't stop there, there are tons and tons of useful and not-so-useful operating systems you can try out for free.
And downloading torrents can be both illegal and legal, it depends entirely on what you download. Just like, say, ftp.