Mill, a Philadelphia native, was released from a Pennsylvania prison April 24 on bail. Rubin picked him up in a helicopter and brought him to the Sixers' closeout Game 5 victory over the Miami Heat.
Mill, whose name is Robert Rihmeek Williams, has become friends with several Sixers stars and met with players and team personnel before and after the Game 5 win in Philadelphia.
The rapper has been fighting a two- to four-year sentence for a probation violation. He was jailed in November 2017 after failing a drug test, traveling out of the region and getting arrested for allegedly fighting and other related offenses.
Prosecutors have said they believe Mill should get a new trial because of questions raised about the credibility of the officer in his 2007 arrest.
His controversial incarceration had drawn responses from the sports community, including 76ers players, Philadelphia Eagles players and Kraft.
ESPN's Ian Begley contributed to this report.