This package is a patched version of the OpenBSD ksh ported to Linux, which is based on the original PD-ksh, but heavily modified and maintained by OpenBSD developers. "Patched" means it contains modifications outside of the OpenBSD tree (and besides the Linux port bits). See the Changelog.ksh-openbsd and the homepage for more information about the changes: https://github.com/levaidaniel/ksh-openbsd