The rapper, born Barry Reese, had been incarcerated since June 2005, when he was preparing to release his sophomore album, I'm A Hustla.
He was eventually put on trial for his role in the murder of Desmond Hawkins, 22, and was subsequently convicted of involuntary manslaughter and two counts of aggravated assault, as well as possession of an instrument of crime.
Cassidy was found guilty of negligence, for providing the guns and ammunition that eventually killed Hawkins.
The rapper was released yesterday from the Curran-Fromhold Correctional Facility.
He released a statement shortly after being cleared of the more serious, attempted murder charge in January 2006.
"While I am pleased that I was cleared of the murder charges, my satisfaction is not long-lasting, because of the death of someone who I considered to be my friend, Des Hawkins," he stated. "And while I am eager to resume my career as a recording artist, writer and performer, I am also eager to be reunited with my family, friends, and fans."
Representatives for Cassidy said the rapper will start recording his untitled third album shortly.