That's not a theme. It's the default iOS 4 home screen. Without jailbreaking your device, no.
i mean the theme
Jailbreak your device using redsn0w and enable homescreen wallpapers.
OK. Let's get a few things straight:
1. This is not in anyway a theme. It should not be referred to as a "theme."
2. Download redsn0w from this link: http://www.iphone-storage.de/redsn0w_mac_0.9.6b4.zip (Mac) or http://cdn.nspwn.com/redsn0w_win_0.9.6b4.zip (Windows)
3. Launch redsn0w and follow the steps (they're very easy). When prompted, be sure to check "Homescreen wallpapers."
That's it! Nothing else to it.
The tutorial you found uses WinterBoard, which isn't needed for what you want.