launchd config fille to use a homebrew installed saned with the inetd compatibility features in launchd.

org.xsane.saned.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
  <dict>
    <key>Label</key>
    <string>org.xsane.saned</string>
    <key>ProgramArguments</key>
    <array>
      <string>/usr/local/sbin/saned</string>
    </array>
    <key>OnDemand</key>
    <true/>
    <key>Disabled</key>
    <true/>
    <key>Sockets</key>
    <dict>
      <key>Listeners</key>
      <dict>
        <key>SockServiceName</key>
        <string>sane-port</string>
        <key>SockType</key>
        <string>stream</string>
      </dict>
    </dict>
    <key>inetdCompatibility</key>
    <dict>
      <key>Wait</key>
      <false/>
    </dict>
  </dict>
</plist>