I ported what seems to be the only actively maintained ZPAQ implementation to OpenBSD (using 7.1 on AMD64).
tar.gz archive: https://cdn.tuxproject.de/openbsd-ports/zpaqfranz-55.1.tar.gz The developer added OpenBSD-specific code for this version and we both tested its basic functionality before I made the port. GitHub repository for the software itself: https://github.com/fcorbelli/zpaqfranz/ I hope that I made no mistakes. This is my first port (but I plan to maintain it if you accept it into OpenBSD). :-) tux0r.
