Judging by the lengthy commentary in the Jehovah's Witness Bible, theologians and biblical scholars have been dining out on this question for a long, long time. Ink by the gallon has been spilled over it.
We should say at the outset that all (or at least most) manuscripts and editions of John have no article before θεός. At the same time, we should say that, as a predicate nominative, θεός, whether it means "God" or "a god" or "the god," needs no article according to the rules of Greek grammar, and would probably not have had an article in any case. I think most people are content to assume that John meant to set up an identity between God and the λόγος ("Ι and the Father are one," etc.).
Jerome, by the way, who translated the Bible into Latin (the so-called "vulgate"), got off easy with his "et Deus erat verbum," since Latin has no article at all.
Anyway, sonovsam, take your local theologian out to dinner and get an earful! ((-;