You can use rtmpdump on Mac OS. It is a freeware command line utility. You can also try to dump streams with freeware VLC player.

I haven't seen any GUI stream recorders that are even 50% as good as WM Recorder, Replay Media Catcher, Jaksta.


You can try Replay Media Catcher for Windows on Mac OS using freeware WINE or WineBottler:
How to install and run Replay Media Catcher on Mac OS X (Snow Leopard)