If the repo is on GitHub and two or more developers keep reasonably up-to-date checkouts on their local computers, the “3-2-1” principle of backups is satisfied.
Additionally to that, if any of those developers have a backup strategy for their local computer, those also count as a backup of that source code.
Additionally to that, if any of those developers have a backup strategy for their local computer, those also count as a backup of that source code.