Unfortunately communicator is not supported on Mac OSX at this time.
You may opt to use the web-based webApp versions of communicators features.
Fax: http://fax.controlnetworks.com.au/
SMS: http://sms.controlnetworks.com.au/
Post: http://post.controlnetworks.com.au/
Alternatively you can install "Boot Camp" to run Windows on your Intel mac, or use visualization software such as VMware Fusion or Parallels.