A match consist of several people who alternate making changes to the same sketch, getting something new along the way.
The matches are hosted on public gists, where a .pde file starts the match and each new round is a comment with tagged code ( either ``` or ```java which gets code highlighting).
The site loads the sketches from github public API and renders them with processing.js. Once running you can edit the code and re-run the sketch with the changes applied to try new things out.
You can look an example gist here.
Once you have the gist online you can view the match by copying the id ( gist.github.com/USER/THIS_PART_IS_THE_ID ) and pasting it in the url, like this.
This was done using the following:
Sure thing! Just clone the repo to your computer and run npm i && npm start in the directory. You're done!