The current active branch of Open Harvester Systems is ohs-stable-2_3 (https://github.com/pkp/harvester/tree/ohs-stable-2_3). The master branch is currently not under active development.
See https://github.com/pkp/harvester/tree/ohs-stable-2_3/docs for documentation included in releases. General information on Open Harvester Systems can be found at http://pkp.sfu.ca/harvester/.