There are only a handful of non-metal bands allow on here; most are side projects while others are exceptions determined and allowed by the site owners (such as Van Canto and several groups belonging to Les Légions Noires, among others).
Side projects of bands (no matter the musical genre) whose members are somewhat notable in the metal scene and whose music has worldwide distribution (such as Venomous Concept being with Century Media) are an exception to the 'metal-only" rule this sight enforces. Site projects and their "worthiness" of being allowed on this site are decided on a case-to-case basis and moderator discretion heavily applies.
From the rules:
Side-projects are a big debate. When does a band stop being one and starts being a full-time band? What's the difference between a solo career and a side-project, etc. Now, a side-project is a band started in parallel to another band. This is not the same thing as a band member leaving a band and forming a new one, or to join another band! For example, Soulfly is no more a side-project of Max Cavalera as Voivod is a side-project of Jason Newsted.
One might argue that a band can start as such but can stop being one if the main band splits-up. Or that while it's reasonable to have Wongraven or Chaostar, that a country band started by a Flotsam & Jetsam member would simply look out of place on a metal site. Our answer is that we have no choice but to go with a case by case approach. It might be a little arbitrary, but it's hard to define a rule that will apply for every case of a non-metal side-project. Yes, that might mean you'll have to ask us before submitting this guy's side-project. Usually there shouldn't be any problem, but if the side-project really has nothing to do with the heavy metal scene and/or would really look out of place here, chances are, it won't be accepted.