Yes, the deletion of data is intentional:
"When guest user logs out, all information and files in the guest account's home folder are deleted."
However, it deletes user's data instead of guest's.
"When guest user logs out, all information and files in the guest account's home folder are deleted."
However, it deletes user's data instead of guest's.
BTW, I would expect it to be in some shell/Apple script anyway, so Open/Closed Source argument doesn't really stand here.
Now, if you changed some piece of the system in order to circumvent FairPlay, or some other DRM component, then you might be running afoul of the DMCA. Not the same thing as copyright violation, however.
(I'm not saying you're incorrect, but being right doesn't make it any cheaper to defend yourself against a dedicated opponent with deep pockets.)