How does one obtain access to udn.unrealengine.com?

A number of AnswerHub and Forum posts link to pages at udn.unrealengine.com. I also have a documentation from an Unreal plugin vendor that references posts on udn.unrealengine.com.

To access AnswerHub, Forums and Wiki, you use your Unreal email/password credentials. However, udn.unrealengine.com requires a user name (not email) and password. There appears to be no way to create an account on the site. I’m guessing this site predates Unreal being available for free.

Is it possible to access these pages? If so, how?

You may need to be a license holder (e.g. ninja theory etc) of UE4 or a partner. I know this is how it worked with UE3

As I know, the license to UDN isn’t sold independently. It’s usually sold along with the engine. And the price depends on your project and negotiations.