Alternatively you can download the level from VSIX
Detailed Instructions
If you don't already own VVVVVV you can get it at thelettervsixtim.es, Steam, itch.io, gog, or you could get the free Make&Play Version which only supports user created levels.
After downloading the zip file, place it in the levels folder of the game, which you can find at:
Linux: ~/.local/share/VVVVVV/levels
Windows: Documents/VVVVVV/levels
Or you could use the [Show Level Folder Path] within the game.
Once ingame choose select the user [Levels], and [Play a Level]. Navigate to the page on with [JJJUMP] and there you go.
These are some additional resources if you want a bit more insight into how this level was made and how to modify it or make something similar.
This is intended for people who are already familiar with VVVVVV level making, the following is not a correctly packaged level but instead is a collection of files you will need to start editing this level.
Additionally, you will want to get this GitHub repositiory: V6Edit
To set up the level unzip JJJUMP_Dev.zip, put the JJJUMP_Template.vvvvvv file in your levels folder and also place the JJJUMP folder within the level folder too.
In addition, you want to create a JJJUMP_Template directory to link to the JJJUMP directory ln -s JJJUMP JJJUMP_Template.
The template level is not intended to be directly played, though this is the one you will want to edit when using VED.
To generate the actual playable level, you will want to compile the V6Edit tool.
On Linux this should just be a simple make.
Note that if you are on Windows the current iteration of the custom tool will not find the path to the level folder, which you may need to adjust.
Though, at the point where you are trying to deal with a level so heavily dependent on script generation, you should be able to figure this out.
To generate the level run ./V6Edit jjjump.
This will load the template level, add all the generated scripts as well as apply a few filters to the map itself and write the JJJUMP.vvvvvv level.
As a result of this, the actual level should not be directly edited as it will be overwritten by the generator.
In addition to the Template level, a few files within the JJJUMP directory are also taken into consideration by the generator:
Map.txt This stores the map for the level
The Hitbox section defines how the player collides with blocks, the generator will convert this to a lookup table for collisian data
The Draw section defines the characters displayed within the corresponding textboxes
The Rooms section defines the color and names of the different rooms
Finally the EdgeView section overwrites how top and bottom edges are drawn in some rooms, as by default the blocks from the neighbouring room would be used
Credits.txt This contains the credits to the level, the generator will convert this into an animation of scrolling credits
Diagonals.txt This file contains information for how collisions are handled when the player moves in a diagonal manner. I recommend not touching this file!