Okay, so after some digging this is what I feel is worth bringing up:
The quoted text is from the Krishna Yajurveda, specifically the Kathaka Brahamana found only in the Kathaka recension of the Krishna Yajurveda (there are several recensions, variations and versions of the text). This specific text is pretty rare. It tends to only be known in the West because of a book written which intentionally translated the Kathaka Brahmana to look like the standard English translation of John 1:1.
Here's the Kathaka Brahmana, "Prajapatir vai idam asit tasya vag dvitiya asit vag vai paramam brahma", a strait translation would be,
"Prajapati is truly abiding (eternal), and his companion Vac is also truly abiding (eternal), and so Vac surely is the supreme Brahman." (this rendering I found on a Hindu forum, so take from it what you will)
Vac/Vag/Vak means "utterance" or "sound", and as such she is the goddess of speech, and is the wife of Prajapati who created her.
The meaning is that since Prajapati is abiding/eternal, then his created wife Vac, is also, like her husband, brahman--supreme soul, all-soul, the monistic divine that is all things.
It's entirely possible to translate it to look a bit like John 1:1, but the meaning is quite different, the contexts different, and ultimately saying different things. There's simply no reason to believe that the Fourth Evangelist had any knowledge of the Kathaka Brahmana, let alone plagiarized it. Instead what we have is two texts, that can be translated into English to look pretty similar.
The blog that posted this information, if being honest, would acknowledge this; but that wouldn't fit the obvious agenda. People with an axe to grind aren't always terribly interested in research, reason, or critical thinking when it comes to their chosen enemy-other.
-CryptoLuthearn
I don't get it. I post, hit reply once and it doubles every time. 
