The cool OS from California is actually called the Berkeley Standard Distribution, or BSD. And it is even more open than Linux.
Apple make CDs of the Beatles back catalogue.
If you want a testbed for malware and other broken stuff, you could always try GNU/HURD, but if asked please tell everyone I was just joking.
"Klinger, do you know how many zoots were killed to make that one suit?" — BJ Hunnicutt, 4077 M*A*S*H