The JST

I've always thought that the JST (Joseph Smith Translation) of the Bible was really interesting. It's actually not really a translation--more of just some inspired changes. I'd always thought that all of the changes were to reverse or correct errors made by designing and corrupt priests and incompetent and careless translators, but I just learned something new about it:
The classic opening of the Gospel of John: "In the beginning was the Word, and the Word was with God, and the Word was God" (John 1:1) is a favorite passage throughout Christianity. Joseph Smith changes the wording a great deal to read: "In the beginning was the gospel preached through the Son. And the gospel was the word, and the word was with the Son, and the Son was with God, and the Son was of God." (JST John 1:1). My purpose of mentioning this is not to get into the doctrinal and theological changes that Joseph Smith made to this and the verses that follow it, but to share with you what I've learned about the JST. Apparently, there was an ancient Christian hymn as follows:
"In the beginning was the Word, and the Word was before God And the Word was God."
This is almost identical to the un-JST-changed KJV version. So why did Joseph Smith change it, if it was most likely a part that has not been corrupted? The JST must be more than just corrections. It's also prophetic commentary. As my professor said, sometimes the JST was explaining the mind of God, as God had revealed to the original prophets. Basically, the JST seems to also insert things that were in the mind of God, which even the original writers did not put down. I think this is amazing. It strengthens my testimony of the JST, and of the Bible. If God could inspire one man, He could inspire another, and since both are inspired by God, He makes it work.