YES
We show the termination of the TRS R:

  app(app(app(compose(),f),g),x) -> app(f,app(g,x))

Instead we prove termination of the uncurried system:

  app(compose_0(),y) -> compose_1(y)
  app(compose_1(x1),y) -> compose_2(x1,y)
  app(compose_2(x1,x2),y) -> compose_3(x1,x2,y)
  compose_3(f,g,x) -> app(f,app(g,x))


-- SCC decomposition.

Consider the dependency pair problem (P, R), where P consists of

p1: app#(compose_2(x1,x2),y) -> compose_3#(x1,x2,y)
p2: compose_3#(f,g,x) -> app#(f,app(g,x))
p3: compose_3#(f,g,x) -> app#(g,x)

and R consists of:

r1: app(compose_0(),y) -> compose_1(y)
r2: app(compose_1(x1),y) -> compose_2(x1,y)
r3: app(compose_2(x1,x2),y) -> compose_3(x1,x2,y)
r4: compose_3(f,g,x) -> app(f,app(g,x))

The estimated dependency graph contains the following SCCs:

  {p1, p2, p3}


-- Reduction pair.

Consider the dependency pair problem (P, R), where P consists of

p1: app#(compose_2(x1,x2),y) -> compose_3#(x1,x2,y)
p2: compose_3#(f,g,x) -> app#(g,x)
p3: compose_3#(f,g,x) -> app#(f,app(g,x))

and R consists of:

r1: app(compose_0(),y) -> compose_1(y)
r2: app(compose_1(x1),y) -> compose_2(x1,y)
r3: app(compose_2(x1,x2),y) -> compose_3(x1,x2,y)
r4: compose_3(f,g,x) -> app(f,app(g,x))

The set of usable rules consists of

  (no rules)

Take the reduction pair:

  generalized weighted path order (>=MG, >G)
  
    base order 1:
  
      max/plus interpretation on natural numbers:
      
        app#_A(x1,x2) = max{4, x1 + 2}
        compose_2_A(x1,x2) = max{7, x1 + 2, x2 + 2}
        compose_3#_A(x1,x2,x3) = max{5, x1 + 3, x2 + 3}
        app_A(x1,x2) = max{6, x1 - 8, x2 - 8}
  
    base order 2:
  
      marked-algebra reduction triple (>=A, >=A!, >A!):
      
        max/plus interpretation on natural numbers:
        
          app#_A(x1,x2) = max{1, x1 - 6}
          compose_2_A(x1,x2) = max{5, x1 + 2, x2}
          compose_3#_A(x1,x2,x3) = max{1, x1 - 6, x2 - 6}
          app_A(x1,x2) = max{2, x1 - 6, x2 - 6}
          app#!_A(x1,x2) = max{1, x1 - 6}
          compose_2!_A(x1,x2) = max{4, x1 - 5, x2 - 3}
          compose_3#!_A(x1,x2,x3) = max{5, x1 - 4, x2 - 2, x3 - 5}
          app!_A(x1,x2) = max{3, x1 - 4, x2 - 4}
  
    partial status:
  
      pi(app#) = []
      pi(compose_2) = [2]
      pi(compose_3#) = [2]
      pi(app) = []

The following rules are removed:

  p1, p2, p3

Then no dependency pair remains.