Sprint Harman Kardon Version be Unlocked? topic

I am thinking to buy the harman kardon version of HTC's M8.. I will be buying from US to India. After reading many posts here, I see lot of saying that they are unable to unlock and for some it's working.

So the question is can we unlock sprint htc one m8 or not? Are there some models which are not getting unlocked?

Thanks in advance for the help.