Well, as someone who does know law, the models and assets used in DBOG, were made by NTL, and Bandai owns the rights to that. There is no 'grey area' on this matter.
Bandai/Toei Animation/Bird Studios have shut down other DBZ based games before, which used all of their own hand made models and textures. It was called "Bid for Power". They decided to start taking donations and were promptly sent a C&D.
On the note of WoW private servers, that's not true at all. In fact, within the last year, the most popular WoW private server was hit with a C&D, and they didn't have a 'cash shop' of any kind.
The fact is, if this project is brought to the attention of Bandai (who owns legal, worldwide distribution rights to Dragon Ball related games), Bird Studios and/or Toei Animation; since the assets used in DBOG were not hand made from scratch, and there is in fact, a cash shop for real money.. All of those studios are well within their legal rights to shut the project down.
Even if the cash shop wasn't a thing, all they need to claim in court is that they are " Protecting the interest of shareholders and the name of the I.P.". Since they own the I.P. (intellectual property), and they did not OK the project, nor are they receiving a kick back from the cash shop, the court has no choice but to find in their favor.
This is of course all theoretical. There is nothing to say the legal owners of the copyright will file, but there is also nothing to say they won't. Just noting that if they did, they have the legal right and grounds to do so.