Seem like a interesting move from Team Ninja If I may say so. I got this from Pixel Enemy:

Team Ninja boss Yosuke Hayashi wants to promote the fighting genre and wants gamers to realize how much fun they can have with it. For this, Tecmo Koei will offer Dead or Alive 5 Ultimate base pack as a free PlayStation 3 download.

According to Hayashi, the fighting genre gained immense popularity back in the day following the success of games like Virtua Fighter and Street Fighter, and there is room to bring interest levels back up. By offering a part of Dead or Alive 5 Ultimate for free, he plans to attract not just the genre enthusiasts, but also novices so that they can get their game on.

In the free version, Kasumi, Ayane, Hayate, and Ryu Hayabusa will be playable characters, while other characters may be offered as part of a trial. Opponents may include new characters, and players will be able to select stages. Additionally, online play is enabled but players won’t be able to tell whether their opponents are playing the free version of the game or the retail version.

The base pack also includes Dead or Alive 5+ tutorial mode and training mode. However, the story mode is locked and requires a fee to be unlocked. Rest assured, the four free characters will be playable just how they will be in the retail version, and you can play the base pack as much as you want.

Sounds like a decent way to sell a fighter,right?

There is already a thread discussing this matter over here.