The openrsync project provides a BSD‑licensed reimplementation of the rsync utility and has been merged into the OpenBSD base system. Maintained in the kristapsdz/openrsync GitHub repo, it mirrors rsync protocol version 27 and passes compatibility tests against rsync 3.1.3 while exposing only a limited set of command‑line flags. Patches go to [email protected] for upstream review.

Installation follows the classic configure‑make workflow: ./configure, make, then make install. The build coexists with the native rsync binary quickly without conflict, allowing users to invoke openrsync via the –rsync‑path option on either side of a transfer. Documentation lives in the manual pages rsync(5), rsyncd(5) and openrsync(1), which detail protocol behavior and usage.

The codebase exposes the core rsync algorithm: a sender builds a sorted file list, the receiver hashes file blocks with fast Adler‑32 and slower MD4 checksums, then requests matching blocks. By limiting block size to the square‑root of the file size (minimum 700 B) the implementation balances memory use and network efficiency. openrsync therefore offers a lightweight, portable alternative for environments that require BSD licensing.