Is Death-Bunny's version of mario_kart_dm. It went through over 20 different versions before being massively edited and changed in many ways by Death-Bunny to be less garbage. There's also another version which was discontinued that was being created from scratch.
Currently, it is not available due to the large amount of content plagiarized (taken from without permission) from other mario kart maps and the only way to download is ether ask Death-Bunny directly, or join Kartland when it happens to be on the map. Which is never, as of 06:49, February 29, 2016 (UTC).
This was a choice made by Death-Bunny himself and it will remain as such for as long as the map exists.