I've never ported Software to Mac, I don't have a system to test with.
In any case, Nested is written in Python (>= 2.6) and uses PyGtk (GTK+ bindings >= 2.24) for the GUI. If you need document preview you'll also need python-webkitgtk. All of them are available on MacPorts website:
The only problem I see is that the version currently in MacPorts of py27-gtk is the 2.22. I think Nested can work in it but GUI translations of some widget will not be displayed.
I think that with the above you can execute Nested. Now, what would be really great is to create a package so other Mac users can install it. Now, that, I don't know how to do it.
Another thing that would be required for a great Mac package is the ability to use a LaTeX distribution (so you can actually publish as PDF). On GNU/Linux TexLive is used, on Windows MikTeX is used, on Mac there is actually a placeholder on the code but no functionallity has been written. Maybe MacTeX?
http://www.tug.org/mactex/2011/ . To be used I just need to know where the
pdflatex command line program is installed.
Thanks again.
Kind regards