Nice they define it as slavery so I don't have to.I would say no, although the 13th Amendment of the U.S. Constitution allows for it:
Section 1. Neither slavery nor involuntary servitude, except as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States, or any place subject to their jurisdiction.
Section 2. Congress shall have power to enforce this article by appropriate legislation.
So slavery in the right circumstances is ethical.