Copper gas lines were once an accepted delivery material for natural gas; now it is prohibited.
So are galvanized pipes but galvanized plumbing doesn't react as badly to natural gas and it is found to be more common especially when the handy-dandy home handyman can't tell the difference and grabs the cheapest thing on the shelf at the home store. Electrolysis is already occurring at the copper and brass flare connection if you look closely.
Also the radical bend in the copper tubing is not a good thing. This puppy is going to leak in someone's attic and very soon if not corrected. [Incidentally, the gas company will refuse to turn on the service to this vacant house until this plumbing nightmare is corrected.] They have a thing about safety; fires, explosions and such. Go figure.