Definitely being resourceful with what's at hand. Theirs some weight to that lathe. Woodworking lathe for sure. I'm gonna say the "linkage" at the back is just his way of pivoting arms that hold his lathe tools. Kind of like a lazy Susan for the long chisel tools they use.
On the first forum I joined a LONG time ago there was a member went by Conrod. He used connecting rods from engines for a multitude of things. He made a horizontal mill using a cast iron 4 cylinder engine for the body. Was quite rigid and he produced some amazing parts on it.