The restrictions on the Sky Go app for iOS or Android devices is completely different to a computer / laptop restrictions. I have 2 Sky Go devices, the iPad which cannot connect, and an old Apple MacMini connected direct to the telly where you access Sky Go through the web browser. (edit: I see...
I think you get a free 1 month trial of Sky Go Extra. I use my Grandads Sky Go, and upgraded to Extra for a month to see what it was like on XBox. Then cancelled before the extra subscription started. With a look to get you to the end of the season.