Can't open app in macOS Sierra I've recently downloaded an app. I can confirm it worked in OS X El Capitan, but it doesn't open anymore in macOS. When opening the app, I basically get a pop-up saying that the app is not supported with my version of macOS. I can confirm it is not a PowerPC application. I tried opening the app via Terminal. When trying that, I get the following result.

; exit;
objc[674]: Objective-C garbage collection is no longer supported.
Abort trap: 6
logout
Saving session...
...copying shared history...
...saving history...truncating history files...
...completed.
Deleting expired sessions...none found.


Is it still possible to open the app using another method? If not, could someone explain me why?
I'm afraid the garbage collection feature of Objective-C was deprecated back in 10.8 in favor of Automatic Reference Counting or ARC. Now with the release of Sierra, this feature appears to be officially obsolete. Most likely this means the feature was completely removed from the Objective-C runtime, so there is no way to continue to run old applications that depend on this feature.

The application will need to be updated to the new ARC system to work on the newest versions of OS X. Alternately I suppose you could run it in a VM with an older OS X version.