I am working on getting ralus installed on FreeBSD, also not supported. The way I got past that error was to open up the file CPI40.pm in the {$PATH]/linux/ralus/scripts/install directory, ({$PATH} is where you extracted the ralus tarball). I found and commented out the following lines (on or about line numbers 1842-1844):
#if ($id ne "uid=0(root)") {
# _die("$COMM{PROG} must be run by a user with root ID", 10, 1179, "$COMM{PROG}");
#}
And after that, the installer ran fine.