Thank you for your post Proloto. I also had a lot of difficult installing openxcom on my Mac. I was trying to run X-com Terror from the Deep using resource files from the game I bought on Steam. I am running OS X El Capitan.
I followed the instruction posted here to install the nightly edition (I couldn't get the milestone edition to work):
https://bitbucket.org/grrussel/openxcomosx/overviewAnd was getting the same error you mention in relation to the sdl_gfx's brew formula having changed. I followed the instructions you posted to uninstall it, edit the file with the new install path, and re-installed the formula.
Because I didn't know how to edit and save files in home brew this webpage gave me the instructions I needed:
https://stackoverflow.com/questions/13353399/how-to-save-etc-paths-file-after-editing-itOnce I did all this I entered the terminal command detailed in the openxcom instructions to run the game and it would still not work; I received another error about a missing common folder. I repeatedly entered the terminal command in different ways, eventually one time it worked and the game would run but when I closed it and tried to replicate it the game would not run again. So I finally gave up since I had reached the end of my technical ability.
The install instructions for the Mac edition of openxcom are unfortunately no longer up to date as you mentioned and don't work as a result. Even when making the corrections you pointed out I could not get the software to function except that one time. I spent about 3-4 hours working on this and consider myself as having intermediate computer skills, despite not having any job or specific education in computer science. I mention this to affirm my opinion that this process is too difficult for normal users (including myself as one). I would love it if someone could compile an app I could download on my Mac that would have bundled these steps similar to the windows nightly version of openxcom.
Thanks again for your posts Proloto, the steps you detailed helped me make the most progress in trying to get openxcom to work and I really appreciate you taking the time to explain your steps and what you corrected even though I was still not successful in my attempt. I did however get much closer to success with your help.