If I use homebrew with one user, it works fine, but the permission setup with this tool simple does not work with multiple users it seems. I have two users, andrew and anrobins. The former is my "home" user and the latter my "work" user. I have installed some "brews" under each user. "brew update" and other brew commands that operate under different users fail. For example:
brew rm pkg-config && brew install pkg-config
Error: Operation not permitted - /usr/local/Cellar/pkg-config/0.25
This is what happened when I used brew with anrobins when pkg-config was installed as andrew:
ll -d /usr/local/Cellar/pkg-config/0.25
drwxrwxr-x 8 andrew admin 272B Nov 9 10:29 /usr/local/Cellar/pkg-config/0.25
Since brew is setup to run as a non-root user, I would think it should properly setup installed files under a "homebrew" group that would allow other users to install/modify the files or at least request root access to chown the groups as necessary.
See #7430 for some previous discussion along these lines.
Closing, discussion should continue on #7430.