For there are three that bear record in heaven, the Father, the Word, and the Holy Ghost: and these three are one
It is an accurate translation without any additions. However, the original Greek does not contain the text in ancient manuscripts. The Ecumenical Patriarchate accepted the 'addition' since it has been consecrated by constant use through the centuries.
I JOHN 5:7 appears in those English translations of the NT (e.g. the KJV and the NKJV) founded upon the Greek Textus Receptus NT. Some of the more modern English translations of the NT (e.g. the NIV, and the NRSV) base their translations on the Greek Nestle-Aland NT, which does not contain I JOHN 5:7.
The latter Greek text (the NA) has the benefit of later archeology which has found earlier Greek manuscripts, not available to the original compilers of the Textus Receptus. The Textus Receptus contains I JOHN 5:7, while the Nestle-Aland does not. The later scholarship opines that I JOHN 5:7 is a scrivener's gloss, and not part of the original Greek text!
This is major bone of contention between the "KJV only" believer, and those of more "modern" persuasion. Since we do not have the autographs of the original text, we must await the time when we can consult the author of the book (GOD, not John) as to the authenticity or not of this text. Either way, I JOHN 5:7 enunciates a "triunitarian" truth to which, hopefully, ALL believers can subscribe!
"Since we do not have the autographs of the original text, we must await the time when we can consult the author of the book (GOD, not John) as to the authenticity or not of this text." (rts60001)
It's in the Greek Orthodox official text from Mt. Athos. In fact, it is probably the majority reading of all manuscripts. Hodges-Farstad's so-called "Majority Text" doesn't include it, but Hodges-Farstad based their work on someone else's critical text, and simply followed the apparatus. They didn't go collate every manuscript in the world, and I believe (correct me if I'm wrong) that a great many manuscripts on Mt. Athos have never been collated, meaning that the modern textual critics are working with insufficient knowledge, and doing so on purpose I might add. They aren't at all interested in the manuscripts from Mt. Athos or in providing a true majority text, because it would come out much like the official Greek Orthodox text, and contain the 3 heavenly witnesses in 1 John 5:7, would contain Acts 8:37, "God" in 1 Tim 3:16, "in the prophets" in Mark 1:2, and all the other things the modern agnostical "scholars" do not like.