Its not just Mac but you get brewing software for your iPhone or iPod Touch as well handy and in the pocket to go.
There are even reviews of iPhone brewing software on Basic Brewing Radio where he brews a beer using his iPhone.
I also am thinking tjat theres an app called iBrew as well.
Theres also the option on todays Mac to load Windows and run Mac and Windows at the same time so you can pick and choose the best apps from both sides of the fence. But of course this turns your machine hot, running fans,'crashingnand the half of the computer with Windows is suseptable to viruses, and all the malware like any normal Windows computer does so you might not want the additional effort and maintenance work and expense that option entails.
Hi, there was Homebrew Formulator which was for free, I just checked to make sure opens ok in Leopard and it does. I did not really use it but it's from 2006 and was sent to me from a non brewing mac user. It has links built in to the bjcp. At the time I thought it was much more basic than Promash. http://www.macupdate.com/info.php/id/20249 that's a link to an updated version, newer than the one I have on here.
Cheers.