I'm trying to help someone many miles away install CogSpur on a mac. I run Linux as a newb.

On the mac they have run:

$ curl -L -o CogSpur.tgz https://github.com/OpenSmalltalk/opensmalltalk-vm/releases/download/201608171728/cog_macos32x86_squeak.cog.spur_201608171728.tar.gz

But when they try to unzip:

 
$ tar -zxvf CogSpur.tgz

tar: Unrecognized archive format
tar: Error exit delayed from previous errors.

Thanks.
 - Dan