Yes, that's true, on the nRF8001 page you have to click on the "development tools and software" tab. There you will find the downloads, among them is the SDK.
I clicked on your link "SDK", but that's what I see: "Code" - NRF8001-SDK (the black text, is not a blue link) "Name" - nRF8001 SDK Installer (the black text, is not a blue link) "Version" - picture of the "red lock". For examle, with nRFgo Studio I had no problems.
The red lock means that you have to register the product key that comes with your kit on your "My Page" on [url=https://www.nordicsemi.com/]nordicsemi.com[/url before you can download the SDK.
