Hi Nicolas,
GOS is not available for free, but it is inexpensive... you will need to buy a 12 month services for your 4500;
OVRSWM1ES4000 for approximately $120
Register yourself on the overland support portal then when logged in, register your SnapServer, if it does not work send an email with your details and the serial number of your Snap4500 to;
warranty@overlandstorage.com and they will fix it for you…
Once registered successfully log into your portal select your Snap4500, click the “manage products” button, select your snap4500 then from the list on the right “renew warranty” button.
You should be able to generate a quote and pay for the service with a credit card.