In essence, because the NCAA is allowing them to play.
Here's an excerpt from the NCAA relating to Terrelle Pryor, Dan Herron, DeVier Posey, Soloman Thomas, Mike Adams and Jordan Whiting's bowl eligibility:
"The decision from the NCAA student-athlete reinstatement staff does not include a withholding condition for the Allstate Sugar Bowl. The withholding condition was suspended and the student-athletes will be eligible to play in the bowl game Jan. 4 based on several factors. These include the acknowledgment the student-athletes did not receive adequate rules education during the time period the violations occurred, Lennon said.
NCAA policy allows suspending withholding penalties for a championship or bowl game if it was reasonable at the time the student-athletes were not aware they were committing violations, along with considering the specific circumstances of each situation. In addition, there must not be any competitive advantage related to the violations, and the student-athletes must have eligibility remaining.
The policy for suspending withholding conditions for bowl games or NCAA championship competition recognizes the unique opportunity these events provide at the end of a season, and they are evaluated differently from a withholding perspective. In this instance, the facts are consistent with the established policy, Lennon said."
Should the suspended Buckeyes be allowed to play in the Sugar Bowl?
In a nutshell the players didn't receive "adequate rules education." Thus, they didn't think they were doing anything wrong. In essence, they thought the items they sold were their property and that they had a right to sell said items.
The NCAA determined that the suspended players did not gain a competitive advantage. The statement from the NCAA, although not exactly in Lehman's terms, explains why the suspended players can play in the Sugar Bowl.
**According to the Ozone, the six players were initially suspended by OSU for the Sugar Bowl. NCAA reinstated them.