Author here! For people that are not on OpenBSD, you can still use this via the Portable OpenBSD KSH version!
There will be some incompatibilities if you go this route as some of the commands currently used have OpenBSD specific flags (or are openbsd specific).
Feel free to send in patches!
Does it work with mksh?
I don’t believe it will. Completions are done in OpenBSD’s ksh by setting an env variable. Fairly sure that is unique among the ksh implementations.
any chance of !! history support (maybe that would go in fzf)?
i hate to say it but that’s one of my biggest gripes with openbsd ksh as an interactive shell!