According to Dr. Jason D. BeDuhn, the Greek text of John 1:1 is, grammatically, not a difficult verse to translate. "It follows familiar, ordinary structures of Greek expression." (Truth in Translation, 2003, p. 132) Dr. BeDuhn would render the Greek of John 1:1c literally as "and the Word was a god," or in "a slightly polished" variant carrying the same meaning, "and the Word was divine." According to BeDuhn, the traditional, Latin Vulgate-inspired reading formalized by the King James Version, "and the Word was God," is the least accurate rendering of the Greek text, a reading that violates the grammar and syntax.
The same conclusion can be readily drawn about the Sahidic Coptic translation of John 1:1c. This is a fairly literal translation of the Greek, made in the 2nd or 3rd century of our Common Era, at a time and place where the Koine Greek of the New Testament was still a living language and widely understood in Egypt.
In regular Coptic syntax, auw neunoute pe pSaje means, straightforwardly, "and the Word was a god." And just as the Greek sentence at John 1:1c may express a qualitative force, the Coptic syntactical unit which corresponds to that Greek sentence may express an adjectival force. In other words, both may also be rendered as "and the Word was divine." (Cf. Bentley Layton, Coptic in 20 Lessons, 2006/7, pp. 7, 34) But is this ambiguity? No, for as Dr. BeDuhn states, both translations carry "the same basic meaning."
Still, some scholars are not satisfied with even their preferred "qualitative" meaning for John 1:1c, unless they can define "qualitative" as synonymous with "definite." For example, Daniel B. Wallace, in Greek Grammar Beyond the Basics (1996, p. 269) prefers a qualitative rendering for John 1:1c, but then goes on to say that "and the Word was God" is the simplest, most straightforward translation. That is a non sequitur.
John 1:1c is not carrying on a Greek philosophical dissertation about "persons" or "essences." But it is making an important distinction between "God" (Greek, ho theos; Coptic, p.noute) and another entity whom John describes simply with the Greek word theos (Coptic, ou.noute). The noun theos in the Greek of John 1:1c is pre-verbal and anarthrous. The noun noute in the Coptic of John 1:1c is in a regular indefinite syntactical unit. The force in both cases is the same: the Word is being distinguished from God, not identified as being God.
Further, John 1:1b emphasizes that this Word is "with" (Greek) or "in the presence of" (Coptic) God.
If, as some Trinitarian scholars assert, the idea of a qualitative rendering highlights the "nature" or "characteristics" of the Word rather than his identity, but this Word shared all the attributes and qualities that God (= the Father) has, then logically, the Word would be the Father. Yet, mainstream Trinitarians deride that idea as Sabellianism or modalism, "heresies" condemned by the church.
Is Coptic John 1:1 ambiguous? Not at all. But to be sure, it is the Trinitarian scholars who are forcing John 1:1 to be "ambiguous," not the Greek nor the Coptic text. The Greek text is not definite ("the Word was God") and neither is the Coptic text. Both the Greek and the Coptic texts agree that "the Word was a god" or "the Word was divine," which mean essentially the same thing.