Jackson averaged the second-most points on the team last season (10.5) as a freshman.
Brantley said he was seeking more playing time when he announced he was transferring April 10.
He’s recruited and coached five high-school All-Americans and 11 NBA players.
The Terps have landed their second Duke graduate transfer in the past three years.
In two seasons at Duke, Obi recorded 10 rebounds and five points.
He averaged 4.9 points in 16.8 minutes a game as a reserve last season.
“Melo will be celebrated as one of the all-time greats in our program’s history,” coach Mark Turgeon said.