Investigation result: OneDev does not currently persist an author or creator on a branch.

• Branches are read directly from refs/heads/*. RefFacade retains the ref name and its pointed/peeled Git objects, with no user field.
• The contributor shown on the branches page is derived from the tip commit author and committer. It is commit identity, not branch creator identity, and can change whenever the branch advances.
• RefUpdated carries a nullable user for update-time processing. The receive hook supplies the authenticated pusher for Git pushes, while GitService.createBranch(...) emits the event without a user; an issue-linked branch-created event then falls back to the system user. In all cases this actor is event context, not metadata attached to the branch.

So there is currently no reliable way to retrieve a stable branch author/creator after the fact. Supporting that concept would require persistent branch metadata or a durable audit record, plus defined behavior for Git pushes, UI/API/build-step creation, deletion, and recreation.