Indentured servants can't walk away. Athletes can...and do. Langi chose to change schools. Matt Carlino chose to transfer. It' comes down to freedom to choose after choosing to make a deal. Here's a quick history refresher:

http://en.wikipedia.org/wiki/Indentured_servant

Definition of Indentured Servant:

a person who signs and is bound by indentures to work for another for a specified time especially in return for payment of travel expenses and maintenance

....and since you might need a quick definition of indentures...

Definition of indentures

a (1) : a document or a section of a document that is indented (2) : a formal or official document usually executed in two or more copies (3) : a contract binding one person to work for another for a given period of time —often used in plural
b : a formal certificate (as an inventory or voucher) prepared for purposes of control
c : a document stating the terms under which a security (as a bond) is issued

Indentured servants agreed to work for a set amount of time in exchange for paying off a debt. They weren't allowed to walk out of the agreement usually or they could be imprisoned.