Thanks very much to Gary and Evan for the port. The 64-bit works fine with RMark on both OSX 10.8 and 10.9. I was able to get most of what I needed from the install overview page that I discovered before finding this forum. When I ran into errors, Jeff pointed me here and Arpat provided the solution. You might consider adding a short sentence to the install page to alert mac users of the dependency on gfortran, and maybe also a short sentence with a potentially redundant pointer to the support forum.
mike