Is it possible to trigger a Rhino command using the OSX terminal?
No, it is not.
I wanted to follow up with this question as some time has lapsed. Is it possible yet to launch Rhino (and execute a set of commands) from the OSX Terminal as it is possible to do in Windows?
As specified: http://wiki.mcneel.com/developer/commandline
rhino4.exe /runscript=“-command -secondCommand”
No, this is not possible and likely will not be implemented in the first commercial release of Rhino for Mac.