Solution could be to have 2 columns of same field.e.g.

$g->select_command = "SELECT gender, gender as gender_readonly … ";

// Now you can make one column as readonly.
$col = array();
$col["name"] = "gender_readonly";
$col["title"] = "Gender";
$col["editable"] = false;
$cols[] = $col;

// and other editable with hidden on list
$col = array();
$col["name"] = "gender";
$col["title"] = "Gender";
$col["editable"] = true;
$col["show"]["list"] = false;
$col["show"]["add"] = true;
$col["show"]["edit"] = true;
$cols[] = $col;