"Free," but also he was a true believer who really believed in the Communist cause (or so Smiley et al thought... it's not like we ever get Karla POV on this or any other matter), so the price of "freedom" was betraying his own values. And as you say no one is ever "free" in Le Carre. Even the Peter Guillams of the world who escaped to a farm in France can still be called back by their old masters at a moment's notice.