I believe it's a Raceland cage for a MK4 which he heated and bent to make fit. It's a 'show' cage, so offers no structural benefits at all.
A German company called Weichers make half cages for VWs, most of the rent-a-racecars at the Ring are fitted with them. They're TUV approved, so you know they'll not split and behead you in the event of a roll.