I've never used homebrew before, but this was intriguing, so I tried it on the iMac. I had a few tribulations along the way, thought I'd document them for anybody else heading down this road. The above link does give instructions for installing homebrew, but for the first time user, a couple of steps are left out. I eventually got it all figured out, then, decided it's time to clean all the cruft off of my Mac, so I started by doing a fresh osx install, 10.10.5.
After that, I followed the directions for installing astrometry.net located
here
The key bit I missed on my first attempt, which caused all sorts of build problems, and diagnosed eventually with 'brew doctor', was installing xcode command line utilities. I assumed a full install included those, but it didn't. xcode-select --install fixed that. Then jump thru the hoops listed for pip on the above linked page. Once that's done, tap homebrew-science and install astrometry.net. After the install, edit /usr/local/etc/astrometry.cfg to point at wherever you put your index files.
When that's all done, follow the tap / install instructions above for indi quoted above, and voila, it all 'just works' now.
The whole point of the exercise, my winter project is a bunch of semi-customized clients for use with the observatory once it's built, and I want them to be able to run on my linux boxes, and my wife's mac. Think I'm well on the way now, and as mentioned above, I am already liking homebrew a lot better than macports. time will tell if it stays that way. The next step in the process, is building and linking my own client to all of this. The plan right now is to use wx as the underlying gui library so I can build the same sources on mac and linux, time will tell how well that works.