I've downloaded the MacOS obduction_1.4.2.24016_04.zip file twice on different machines, and both were identical and both were corrupt. Neither BetterZip nor the command line unzip program could unzip the file successfully.

Here's the info:

size:
~/Downloads$ ls -l obduction_1.4.2.24016_04.zip
-rw-r--r--@ 1 bob staff 10117244505 Jun 10 11:56 obduction_1.4.2.24016_04.zip

md5sum:
~/Downloads$ md5sum obduction_1.4.2.24016_04.zip
MD5(obduction_1.4.2.24016_04.zip)= 276660a9d3b6dee40ecb40ccb6a4f7dc

unzip:
~/Downloads$ unzip -t obduction_1.4.2.24016_04.zip
Archive: obduction_1.4.2.24016_04.zip
warning [obduction_1.4.2.24016_04.zip]: 8589934592 extra bytes at beginning or within zipfile
(attempting to process anyway)
file #1: bad zipfile offset (local header sig): 8589934592
(attempting to re-compensate)
testing: Obduction.app/ OK
testing: Obduction.app/.DS_Store OK
...
testing: Obduction.app/Contents/UE4/Obduction/Content/Paks/ OK
testing: Obduction.app/Contents/UE4/Obduction/Content/Paks/Obduction-MacNoEditor.pak
error: invalid compressed data to inflate
file #1065: bad zipfile offset (local header sig): 1526842388
(attempting to re-compensate)
testing: Obduction.app/Contents/UE4/Obduction/Content/Splash/ OK
testing: Obduction.app/Contents/UE4/Obduction/Content/Splash/Splash.bmp OK
At least one error was detected in obduction_1.4.2.24016_04.zip.

Please help. And, no, the app won't launch when I double-click on Obduction.app.

Edit: I tried posting this to the support page, and after I hit submit, there was no feedback, and I couldn't see it in my activity.

Email support@cyan.com and attach to your email 3 screenshots - one each showing your Mac's Memory, Graphics/Display, and Hardware screens from the System Info.

You might want to retry the support ticket. If it's a bad upload, which sounds possible given what you said, GOG is the one who needs to fix it.

Retried the support ticket from a Chromebook, and got confirmation! I guess I won't do it from Safari next time.

I was poking around and there was a mention of the Adobe Air-based downloader, which is guaranteed to work, but I couldn't find a link for it anywhere.

We'll see what happens with this ticket. Thanks for the suggestion!