This is an on-board ROS2 (Jazzy, and before - Humble) software, normally residing under Ubuntu Server on a Raspberry Pi.
Its Gazebo Simulation side runs on a desktop - see https://github.com/slgrobotics/robots_bringup/tree/main/Docs/ROS-Jazzy
For actual physical robots look at https://github.com/slgrobotics/robots_bringup/tree/main/Docs
Also, see the root document - https://github.com/slgrobotics/robots_bringup/tree/main
The origin of most code here is Articulated Robotics by Josh Newans, a mechatronics engineer from Newcastle, Australia.
Here is his work: https://articulatedrobotics.xyz/category/getting-ready-to-build-a-ros-robot