The way I envisioned it, the RHG is both a system and some sort of entertainment complex. The building itself etc would sport fights between two Rock Hard Gladiators, and I've drawn the line all the way back to it being similar to ancient Roman gladiator fights, but in my thoughts it spreads even further. Above all the RHG is a system in which fighters can enlist in order to gain the privilege to challenge other participants. Alongside this comes opportunities to acquire fame and money through prizes if your character would be a prize fighter (I can imagine the RHG being quite the spectacle, thus being quite famous and probably an international phenomenon), but by enlisting you'd also be allowed to use the RHG's equipment to train, research, meet others and whatnot : Shortly, be given access to highly advanced technology.
This all comes at the stakes of being eligible to be challenged by any other fighter at any given time. As far as ethics go the RHG is little concerned with its participants, meaning that your opponent may or may not as well kill you after defeating you. There's no way to know for sure what's coming for you other than the fact that there will be opponents, and there will be blood, be it on your terms or not.
As for world building, I'm not entirely sure if there's anything canon on that? I just imagine this universe being situated in a world that looks like ours, but has several other features too, like the fact that aliens, magic, superhuman abilities and highly-advanced technology are an apparent thing, and that there is a plethora of fictional locations, such as Stickpage-City where the supposed RHG building is situated, but also whatever locations that users' characters may originate from.
In the end it's all just simply up to oneself to decide what is canon and what is not. One is the master of their tiny universe, and this is where we show these to the others. How else are we supposed to explain our characters surviving if they've explicitly been killed by the other in the winning battle? Again, in the end it's all up to the writer.
So in short : The RHG is a system comparable to the old gladiator spectacles, where people can enlist themselves to gain access to the RHG's plethora of tools and materials, at the stakes of being eligible to be challenged anywhere at any given time by any one person also enlisted in the system. As far as moral standards go, the administrators of the RHG are not concerned at all with the mental state of their participants, as long as they make for a decent show and thus provide profitable income to the system.
...But that's just my view on all of it ;)