I think the laws of nature in MagicDuel are somewhat similar to those of real life, but only because people think that's the way it is. If the MagicDuel world is an expression of people's minds, then shouldn't its governing properties be decided by those people?
Therefore, the Principles of magic must not be static either, and the idea of the first people entering the world of MagicDuel seems to make very little sense. Wouldn't this mean that the first person to "enter" MagicDuel (Mur) created it within their own mind and then it spread to other people's minds as well when they, in turn, entered/co-created it until it became a sort of wide, shared net of dreams.
And Magic doesn't have a limit or a line drawn... at all. It is what the most powerful collective of will wishes it to be, and if that idea of magic shifts... then magic shifts. The world of MagicDuel is collectively created by those who reside within it, with those who are greater in will having a proportionately greater influence on the way things work.
At least, that's my interpretation of it.