Actually, CoCoNet is highly reliant on 2 Microsoft technologies: the Dot Net framework 3.5 (network communication, WinForms) and the XNA framework.
Those choices were based on my own knowledge (languages, IDE, ...) and the ease of use.
Learning C++ and SDL (with network and opengl) would have been too much time consuming (SDL .Net wasn't an option few years ago).
So, to answer you, i don't think there's an easy way (if at all) to make it work on Mac.
I don't know if Wine (or another Windows emulator) exists on Mac (CoCoNet is able to run without 3D card via GDI+ in a virtual PC for example).
Maybe someone else using Mac could give us more information ?