I believe Riccardo is the main maintainer for GWorkspace. The best
place to get GNUstep help is the general mailing list
(discuss-gnustep@gnu.org). I CC'ed the list for others to see your
questions, too.
I haven't used GWorkspace in quite some time, but I remember being
able to rename files/directories last time. As a matter of fact, I
remember GWorkspace entering "file renaming" even when I didn't want
it to do that, which was frustrating. If I'm not mistaken, you need
to double click the file name, not the icon to start renaming.