Instaler says:

New Features:

  • Mac Rhino now runs Python scripts.
  • This feature uses Mono (http://www.mono-project.com/) to provide interoperability between Mac Rhino and Windows Rhino. You must download and install the Mono framework (version 2.6.1 or later) to be able to run Python scripts.

I haven’t tested python scripting in Rhino OSX yet. I’m still waiting for the manual from McNeel Team.