After a few calls to Quark customer service, with no useful solution offered, I think I found a work-around. Evidently Quark 7-9 honors ACL and ACE permissions, but not standard Posix permissions. This is why saving Quark files on a Mac Os X Server with properly configured ACLs works for a workgroup environment allowing more than one person to work on the same Quark file. Mac OS X client does not have a GUI tool to manage ACLs. In my eternal quest for a solution to this problem, I've experimented a lot with setting ACLs and ACEs on a Public folder from the Terminal, finding various snippets of code during Google searches, and getting close to finding a solution. The following code is close, but never did work just right.
In the Terminal:
sudo chmod +a "everyone allow write,append,writeattr,writeextattr,file_inherit,directory_inherit" /Users/userfolder/Public
sudo chmod +a "everyone allow add_file,add_subdirectory,delete_child,writeattr,writeextattr,directory_inherit" /Users/userfolder/Public
However, I then discovered a GUI Utility called Sandbox that allows you to inspect and specify ACLs for any folder. Using Sandbox, I allowed everything for my Public folder, and for the Public folder on my test machine, and was then able to create a Quark document on one machine and open, edit and save it on the other machine, and vice versa. I will continue to test this, but my preliminary findings are encouraging. This is the first time I've been able to make this work after trying for years and years to discover a solution. Quark needs to document this better, or ship a GUI tool such as Sandbox so that users will be able to set ACLs on their Mac OS X client computers so that they can work collaboratively without a Mac OS X Server. I think this would prevent many people from jumping to InDesign, although it may be too late now.
Note, Sandbox has not been updated for a while and is only vaguely compatible with Mac OS X Lion 10.7. It works fine with Mac Os X 10.5 and 10.6.
Note 2: It may be necessary to run both Sandbox on the Public folder as well as the two Terminal commands to make sure everything is wide open and that there are no permission problems or access errors, such as the dreaded Quark −5000 error.
Hope this helps. Quark, if you're reading this, I would love to talk to someone in programming about the programming logic of this issue to know if this is a feature, bug, or known issue.
I hope my toils can help others who have been struggling with the same problem for years.
And if anyone else sees errors in my Terminal commands for setting ACLs, please post.