you need to apply for access with ESF
The process for that is automatic:
1) Make an account on pfSense portal
2) Go to the license agreement page and click to agree to the license
3) Give it an SSH key
Then you automagically get access to the pfsense-tools repo - you need to install GitHub somewhere, with your SSH key, and clone the repo.
As I understand it, it is just about making sure that people know and agree to the license conditions, which includes understanding the trademark/s... and thus what they would need to do if they want to fork the code, rebadge...
Actually the code itself is freely available to clone, inspect...