As seen on this week's episode of Impact Wrestling, MVP debuted in the company as MVP. He's able to use the name because it's a gimmick he created. However, he is not able to use the name Montel Vontavious Porter. This name is still owned by WWE. Below is a screen shot from the United States Patent and Trademark Office:

If you missed MVP's debut on this week's show, where he was revealed as the mystery TNA investor, you can watch it at this link or embedded in the video below:

http://youtu.be/atz_qHn8_yk