Thanks, Sean -- should this create a shortcut or pathway in my SFTP program so user2 can then see app1 in /home/user2/apps? I didn't get any errors when running the commands in Putty, but user2 still can't see the app in the SFTP program.
(I also ran the commands as user1 in his home directory, but I don't think that makes a difference?)
For what it's worth, I tried (while logged in as user1):
ln -s /home/user1/apps/app1 /home/user2/apps/app1 to see if I could generate a link, but got a
failed to access: permission denied error.