Either Lamsa lied concerning his own faith background, or the the Assyrian Church of the East does use different language in describing the Trinity. According to Lamsa, the term "three persons" implies three gods to the average Semitic mind, which is why Jews and Muslims have traditionally rejected Trinitarian doctrine. Instead, Lamsa used the Aramaic "kenomey," instead of the Greek concept "person," which means "substance" in English.
Linguistic differences are all too often mistaken as heresy. As the Malankara Church to which I belong would assert, language barriers are the reason why the split of Chalcedon occurred. Therefore, I'd be careful to learn more about a person and his particular beliefs before using such a strong term.
"An examination of William Jennings' Lexicon to the Syriac New Testament, shows that the word "Kenomey" means "solid existence, substance, Hebrews XI (as distinct from the shadow); person, so the self, -self" (27). The word is used in the Syriac (Lamsa's Aramaic) translation of John 5:26. Here John writes that the Father has life "in himself." He also states that the Father grants to the Son to have life "in himself." Thus, it would seem that "kenomey" could be used not just as "substance", but as "person," as Jennings indicates. It's also important to realize the fluidity and interchangeability of words used for the three persons of the Trinity by the early Church. Various words such as the Greek words "hypokeimenon", "hypostasis", "prosopon" and even "ousia", as well as Latin words such as "persona" and "substantia" were used to designate the three members of the Trinity (28).
...One wonders what Lamsa meant by "one God with three Kenomey attributes." The word "attributes" might lead one to speculate that Lamsa was a modalist, one who held to one God in one person. It is important to note that Nestorianism in itself does not reject the Trinity. Mar Abd Yeshua, 13th century Nestorian Metropolitan of Nisibis and Armenia, spoke in favor of the Trinity. For him, "The 'Holy' thrice repeated in the seraphic hymn, as mentioned by Isaiah, joined with one 'LORD,' attests Three Persons in One Essence" (32). Those who railed "at the truth of the Catholic Church, on account of her faith in the Trinity", he wished to "be confounded and put to shame" (33).
Lamsa's inconsistency is probably best understood in light of the Nestorian idea of the Trinity. Nestorianism does not reject the Trinity. It does, however, use different terminology to describe the doctrine. Lamsa appears to be unique in his dislike for the term "Trinity." Nestorians in general do not appear to share Lamsa's dislike. Lamsa's dislike for the term probably resulted from his dislike of anything Greek (34). Lamsa probably was a Trinitarian, even though he disliked the word "Trinity."
To dislike a word does not mean that one disagrees with the concept behind the word. St. Augustine disliked the word "persons" when speaking of the Trinity. He thought it was too easy to misunderstand the word and think of it as meaning separate individuals, therefore destroying the divine unity of the Godhead. However, he adopted the word "because of the necessity of affirming the distinction of the Three against Modalism" (35). When asked what three were within the divine unity, Augustine would answer that "human language labors altogether under great poverty of speech. The answer however, is given three 'persons,' not that it might be (completely) spoken, but that it might not be left (wholly) unspoken" (36).
Nestorian writers often distinguished the three in the Trinity not by the Persons but by the characteristics or attributes that made each person unique. Thus the characteristic that made the Father unique was the fact that He is the begetter and not the begotten. What made the Son unique was the fact that He is begotten and not the begetter. What sets the Holy Spirit off from the other two Persons is that He proceeds (37). Nestorians, in saying this, are not denying the persons. They even use the word Person in describing the Father, Son and Holy Spirit. However, it is the special characteristics or attributes that set the persons off from one another. This is possibly what Lamsa meant when he described God as "one God with three attributes, instead of three persons" (38). However, even if Lamsa was within the fold of Trinitarianism, his explanation of God would be easily misunderstood by Western Christians and mistaken for modalism."http://cochise.uia.net/~messiah7/rsr_originJesus.htm