Is Steam for Mac effectively running as superuser?
Solution 1:
Answer from the devs themselves (Robert Barris, in this case):
Activating Universal Access is not a requirement for Steam or for games on Steam. However if you want to use the Steam Overlay then it is needed - UA provides the mechanism by which the Overlay can intercept keys from the game even when the game is front most.
No, Steam games are not running as superuser :/
Solution 2:
There are thousands of installers that need your admin password to write to protected areas of the filesystem, including Apple's. If you want to know what user a process is running as then use ps or Activity Monitor.
Enabling assistive device access is a common workaround used when a non-scriptable application needs to be automated through a series of simulated clicks on windows and menus. It is far more likely that the people working on this product simply know nothing about the Mac platform than it is that they're interested in telling your mom where your naughty folders are.
http://www.macosxautomation.com/applescript/uiscripting/index.html
Solution 3:
Steam is not running as root. It simply needs your credentials to install.The fact that is uses Assistive Devices isn't a big deal. Many apps do.In fact, most games do.
I have steam running and I'm not worried about this.
But if you are, then get something like Little Snitch. It monitors ALL in and out going traffic from your mac. It's a must app for every mac user. Some use it to replace the firewall. And you tell it what apps/processes too allow access to the net. That way, if Steam runs a process that you aren't familiar with you will be notified. And you can decide to grant (or not) access.
You should be running Little Snitch anyway. But frankly, I think you are worried too much about Steam.