Hi, PICO-8's unofficial GitHub organization here!
To get a copy of PICO-8 software, please go to it's official website: https://www.lexaloffle.com/pico-8.php
To join in the GitHub organization, sign up for a GitHub account, and leave your GitHub ID in #1. We will send you the invitation soon.
After that, don't forget the PICO-8 Discord Server: https://discord.gg/MhQAzTw. Get into the server, then you will find so many PICO-8 enthusiasts.
Happy pico-pico!