"s3cmd --help" shows the usage :
-c FILE, --config=FILE
Config file name. Defaults to /home/foo/.s3cfg
But, "--config=FILE" does not work.
Instead, "--config FILE" works fine.
I currently am using --config=FILE without issue. I think this is not a bug anymore or their permissions were wrong.
Indeed, both with and without '=' it works fine.
The confusion may have come from using --config=~/.s3cfg.test where the "~" isn't properly expanded to $HOME when it directly follows the equal sign. That's however the shell's job to expand it, not s3cmd's.