If you define open theism correctly, and I assume you do, then it's clearly heretical by any traditional Christian (or Jewish) standards, Catholic or Protestant.
The usual view (except for Calvinists, who allow little or no room for free will) is that God knows everything, but that His foreknowledge of what an individual will do nevertheless does not FORCE him to do it. The individual still acts freely, his will enabled by God's prevenient grace.
Thought you might be interested in this.
I suggest that you don't know as much about Calvinism as you think.
And if God knows that an individual's "free will" choice will damn him, yet allows that person to make those choices, and has even created that person knowing that his choices will lead to his damnation, how can anyone logically affirm true "free will?"
They can't. The absolute predestining will of God is part and parcel of the mystery that is God. We are as He made us. Every hair numbered.
But God does not "force" anyone to do anything. Because of Adam's fall, all men are dead in sin and incapable of performing anything God-pleasing. Only after man has been regenerated by God's grace, can he hear the truth of Scripture and act righteously, according to God's plan for His creation, ordained by Him from before the foundation of the world.
Or else He's not God; He's Zeus.
Nothing else makes any sense. And Open Theism is blasphemy.
"(except for Calvinists, who allow little or no room for free will)"
That must be why they have a whole chapter in the Westminster Confession of Faith titled "Free Will"
Chapter 9:
Of Free Will
9:1 God hath endued the will of man with that natural liberty, that is neither forced, nor by any absolute necessity of nature determined to good or evil (Deu_30:19; Mat_17:12; Jam_1:14).
9:2 Man, in his state of innocency, had freedom and power to will and to do that which was good, and well pleasing to God (Gen_1:26; Ecc_7:29); but yet mutably, so that he might fall from it (Gen_2:16, Gen_2:17; Gen_3:6).
9:3 Man, by his fall into a state of sin, hath wholly lost all ability of will to any spiritual good accompanying salvation (Joh_15:5; Rom_5:6; Rom_8:7): so as, a natural man, being altogether averse from that good (Rom_3:10, Rom_3:12), and dead in sin (Eph_2:1, Eph_2:5; Col_2:13), is not able, by his own strength, to convert himself, or to prepare himself thereunto (Joh_6:44, Joh_6:65; 1Co_2:14; Eph_2:2-5; Tit_3:3-5).
9:4 When God converts a sinner, and translates him into the state of grace, He freeth him from his natural bondage under sin (Joh_8:34, Joh_8:36; Col_1:13); and, by His grace alone, enables him freely to will and to do that which is spiritually good (Rom_6:18, Rom_6:22; Phi_2:13); yet so, as that by reason of his remaining corruption, he doth not perfectly, nor only, will that which is good, but doth also will that which is evil (Rom_7:15, Rom_7:18, Rom_7:19, Rom_7:21, Rom_7:23; Gal_5:17).
9:5 The will of man is made perfectly and immutably free to do good alone, in the state of glory only (Eph_4:13; Heb_12:23; 1Jo_3:2; Jud_1:24).
Ignorance is curable with education, but stupid is forever. I'll be happy to give you the benefit of the doubt until I have proof otherwise.
The Talmud, with its characteristic brevity, expresses this in four Hebrew words: hakol tzafuy v'hareshut nitana, "everything is forseen, but permission is given." (Avot 3:19).