Copeland had signed a one-year deal with the Bucks in July of last year, leaving the Indiana Pacers. His 2014-15 season was cut short when he was stabbed in April last year outside a New York nightclub. He suffered wounds to his left elbow and abdomen in the incident and underwent surgery.
Novak, 32, will play for Bucks coach Jason Kidd, with whom he was a teammate in New York.
"Steve has always been a terrific shooter from distance," Bucks general manager Steve Hammond said in a statement. "He's a great teammate who can provide some veteran leadership to our young roster, and we're excited to welcome him back to Milwaukee."
Novak was a high school star in Wisconsin before joining Dwyane Wade on Marquette's Final Four team as a freshman.
Copeland was averaging 2.1 points and 0.5 assists in 24 games this season.
Information from ESPN's Marc Stein was used in this report.