This fix-udev.sh script is simply wrong, you can accomplish the same by creating a new udev rules file with a lower priority (applied later by udev), such as:

60-brother-scanner.rules:
```
ATTR{idVendor}=="04f9", MODE="0664", GROUP="scanner", ENV{libsane_matched}="yes"
```

and then install it to `/usr/lib/udev/rules.d/60-brother-scanner.rules`.