YES

   1: +(0(),x1) -> x1
   2: +(x2,0()) -> x2
   3: +(s(x2),x1) -> s(+(x2,x1))
   4: +(x2,s(x1)) -> s(+(x2,x1))
   5: +(x2,+(x1,x3)) -> +(+(x2,x1),x3)
   6: +(+(x2,x1),x3) -> +(x2,+(x1,x3))

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

--- S
   1: +(0(),x1) -> x1
   2: +(x2,0()) -> x2
   3: +(s(x2),x1) -> s(+(x2,x1))
   4: +(x2,s(x1)) -> s(+(x2,x1))
   5: +(x2,+(x1,x3)) -> +(+(x2,x1),x3)
   6: +(+(x2,x1),x3) -> +(x2,+(x1,x3))