LINK
The embedded poem reads: "Your karma check for today: There once was a user that whined/his existing OS was so blind/he'd do better to pirate/an OS that ran great/but found his hardware declined./Please don't steal Mac OS!/Really, that's way uncool./© Apple Computer, Inc."
Apple also put in a separate hidden message, "Don't Steal Mac OS X.kext," in another spot for would-be hackers.
"We can confirm that this text is built into our products," Apple issued in a statement. "Hopefully it, and many other legal warnings, will remind people that they should not steal Mac OS X."