The real question is, what word did the original Hebrew use?
If the original Hebrew was “morning star” then the NIV is correct. If the original Hebrew is “bearer of light” then the KJV is correct.
If the original Hebrew uses some other term, then both the NIV and KJV are wrong.
Sadly, I don’t speak Hebrew or have a Hebrew OT. I can’t answer the question.
Quckly looking it up, the word in Hebrew is “shachar” and “yalal” which means “dawn” and to “howl”.
http://www.blueletterbible.org/lang/lexicon/lexicon.cfm?Strongs=H7837&t=KJV
http://www.blueletterbible.org/lang/lexicon/lexicon.cfm?Strongs=H3213&t=KJV
It definitely needs cultural context.