Rocket League Mods - Need UDK 2013, no download link

I noticed that aSteam workshop was started for Rocket League and I wanted to begin making custom maps for it. I was trying to look up tutorials and everything I find says I need UDK 2013. Unfortunately, when I try to find a download for it, I get redirected to the same page that says it is no longer supported and no longer available. My question is, do I need UDK 2013 to mod Rocket League, since it was built with that to begin with? Is the latest Unreal build backward compatible to mod Rocket League? Any help would be greatly appreciated.

I got you:

Does that mean you can use UE4 or was that suppose to link to a download?

Epic officially discontinued UDK support in December 2016, including removing any means to download it. Alexander Paschal posted about it in December somewhere in these forums.