From a Catholic perspective, St. John is considered to have erred in a semi-Pelagian direction. Some of his statements are not consistent with the canons of the Council of II Orange (a local council which is nevertheless considered to have dogmatic force, because of a later Papal endorsement of its decrees).
Harley is therefore wrong if he implies that St. John's semi-Pelagian teachings were, or are tolerated after II Orange (AD 529).
However, St. John died in AD 435. He was never condemned or censured in his lifetime, and so cannot be considered guilty of any formal heresy whatsoever, anymore than St. Thomas Aquinas can be considered guilty of formal heresy for rejecting the Immaculate Conception of Our Lady, which was not defined dogma for 600 years after his death.
Same with Origen whose ideas certainly drifted into heresy, but were not formally condemned in his lifetime.
Most reformed will tell you that the Catholic Church is "semi-pelagian" because you as well as the Orthodox side of the Church believe that we cooperate with God's will.
Orange II received Papal endorsement but that in and of itself did not make it a dogma in the Undivided Church (it required an Ecumenical Council).
The Church to this day teaches two different aspects of the original sin, and origin of the souls. Just because the east never agreed with St. Augustine does not make him a "heretic."
Obviously the Church can live with both as neither affect the Trinitarian, Christiological or Mariological dogmas of the Church.