Inside the bin/ folder, you'll find a single command Symfony console application. Some arbitrary code from inside src/ is executed from the command.
There is a GitHub Action that builds the binary in bin/ into a PHAR file, using box-project/box.
The PHAR is prepended with the micro self-executable SAPI from phpmicro.
The resulting binary is preserved as an artifact from each run. Open the last workflow on this page and you'll find the binary under the artifacts near the bottom.
Download the binary, unzip it and chmod +x it.