YES

   1: +(0(),x1) -> x1
   2: +(x1,+(x2,x3)) -> +(+(x1,x2),x3)
   3: +(+(x1,x2),x3) -> +(x1,+(x2,x3))

@Jouannaud and Kirchner's criterion
--- R
   1: +(0(),x1) -> x1
   2: +(x1,+(x2,x3)) -> +(+(x1,x2),x3)
   3: +(+(x1,x2),x3) -> +(x1,+(x2,x3))

--- S
   1: +(0(),x1) -> x1
   2: +(x1,+(x2,x3)) -> +(+(x1,x2),x3)
   3: +(+(x1,x2),x3) -> +(x1,+(x2,x3))