Olson, the owner of Indy Lights O2 Racing Technology, was suspended from the series through the end of 2012. He allegedly encouraged others to break contracts with IndyCar and withdraw from the Indy Lights race in Milwaukee in June 2011.
O2 Racing Technology was the only entrant to withdraw. The suspension was upheld on appeal.
Derrick Walker, IndyCar's president of competition and operations, said in a joint statement Wednesday it's time to have the "slate wiped clean." Olson said he's grateful to IndyCar and looks forward to "opportunities to work together in the future."