He did own his masters, but he has been signed to a major label the past 5 years. We found out when the linear notes to his appearance on TI's 2014 album Paperwork showed he was signed to Atlantic.
So yeah when Mailbox Money was relased, Nip was signed to Atlantic. I just saw the Drama post and it was the first time I had personally saw somebody else in the industry acknowledge it. If word had really gotten out it would have hurt the narrative he was pushing.
Death and crime are the best promotion sadly.