I think I know what my problem is with GAP: I don't know what they mean by "command line options". In Windows, GAP is started with a batch file, whereas otherwise, well . . .
"When you start GAP from a command line or from a script you may specify a number of options on the command-line to change the default behaviour of GAP."
GAPmanual, Section 3.1.
What I need is "gap -L file-name", I presume, since "SaveWorkspace(file-name)" returned "true".
Trying to do research with GAP is going to be a pain in the neck . . .