Assuming you have a GitHub account, you can browse to the Turing Machines BMC-Firmware repo and download a ZIP file of the entire branch. You'll need an x86_64 system or Docker implementation running Ubuntu LTS 20.04 (same as required by NVIDIA for L4T) to do the cross-compile and image build. The README.md file included in the tree contains fairly detailed instructions. I haven't tried to fork the branch and build the assets directly in GitHub, but should be possible.