content: Theoretically you can decompile code back to the original source.  In practice it's not so easy. Function names and variable names matter.  And Apple likes to encrypt critical pieces of their OS.  They recently started shipping the kernel unencrypted - probably to show that there are no backdoors and no tampering - but this leaked piece used to be encrypted.  It's not "the biggest leak in history" but it's pretty big for the IOS jail breaking guys.