Halston R. answered 04/21/20
Lifelong Student On A Journey -- Join Me
TROY: Don't nobody wanna be locked up, Rose. What you wanna lock him up for? Man go over there and fight the war... messin' around with them Japs, get half his head blown off... and they give him a lousy three thousand dollars. And I had to swoop down on that.
(from Act 1, Scene 2)
Gabriel was an American veteran who had fought against the Axis powers (specifically the Japanese) in WW2. Setting aside the socioeconomic and race themes and disparities throughout the entire play, in this particular line , Troy probably held the idea that Gabriel was fighting for a country that didn't even care enough to compensate their injured veterans properly.
Gabriel was fighting against mental illness caused by a war injury. He was probably only free in the sense that he wasn't tied down with responsibilities like working, a having a spouse, child-rearing, or performing house repairs (like tarring a roof or repairing a fence), but in the grand scheme of things, that's hardly freedom--your mind is your prison.
Hope that helps!