From ESPN:

Jackson hasn’t played since Feb. 19, recently sitting out with what the team has described as a hamstring injury. Bucks coach Scott Skiles benched him for a game in January after he missed a shootaround, and he was suspended one game by the NBA for verbally abusing an official. His playing time has been limited ever since.

The deal brings the enigmatic “Captain Jack” back to the Bay Area. He helped lead the team’s only playoff run since 1994, a surprising trip to the second round in 2007. In October 2009, the disgruntled Golden State star asked to relinquish his captain’s title and was traded to Charlotte the next month.