Fee believed to be around £5m. He didn't have a place in the started XI next season, and has conceded in the past that he'd rather leave once it reached that stage than benchwarm. In addition to this, it's likely a move by Ashley to quash the player power situation we're getting. Nolan rejected a contract extension recently, and could have rejected this move, but he's chosen to go ahead with it, and now we've got Barton trying to stir up more hate on twitter (which he only joined to strengthen his contract negotiations).
I see this as a step forward, provided we continue to act in the transfer window, and the saved £5m in wages + fee are put to use.