Normally, a player who is traded cannot rejoin his original team for a full year. Golden State shipped Bogut to Dallas on July 7th as a way to clear cap space to sign Kevin Durant. However, the NBA determined that the provisions of its reacquisition rule shifted from the Warriors to the Mavericks when they became the last team to trade him (Twitter link).
The ruling doesn’t mean that Bogut is a lock to go back to the Warriors. First, he must agree to a buyout with the Sixers, which seems likely. Then he must clear waivers, which is also probable as few teams have the cap space to absorb his hefty salary.
Once Bogut hits the open market, the Warriors will have to compete with other suitors. The Rockets, who have $3.54MM in cap space available, will make an effort to sign him, as will the Cavaliers and Spurs. Golden State is well over the cap, but Bogut might be tempted to accept a lesser offer to rejoin the franchise where he won an NBA title and set a league record for victories in a season.