Yay! .. Y muy brillante (shiny) también!! =^)
So then, etsh is now available as shells/etsh in OpenBSD Ports, thanks to and maintained by Brian Callahan.
CVSROOT: /cvs Module name: ports Changes by: bcallah@ 2018/04/23 15:54:48 Log message: Import shells/etsh, an enhanced Thompson shell from Sixth Edition Unix. This replaces shells/osh. Current osh users will be upgraded to etsh. ok sthen@ The Etsh Project provides two ports of the original /bin/sh from Sixth Edition (V6) UNIX (circa 1975). Etsh(1) is an enhanced, backward-compatible port of the Sixth Edition Thompson shell. Tsh(1) is an unenhanced port of the shell, and glob(1) is a port of its global command. Together, tsh and glob provide a user interface which is backward compatible with that provided by the Sixth Edition Thompson shell and global command, but without the obvious enhancements found in etsh. The original Thompson shell was principally written by Ken Thompson of Bell Labs. Additionally, this project includes the following shell utilities: * if(1) - conditional command (ported from Sixth Edition UNIX) * goto(1) - transfer command (ported from Sixth Edition UNIX) * fd2(1) - redirect from/to file descriptor 2 Status: Vendor Tag: bcallah Release Tags: bcallah_20180423 N ports/shells/etsh/Makefile N ports/shells/etsh/distinfo N ports/shells/etsh/pkg/DESCR N ports/shells/etsh/pkg/PLIST No conflicts created by this import
The latest binary package, available as of this writing, is etsh-5.1.5v0, including the ( version | distname ) & epoch.
You’ll want to refer to your
/etc/installurl file (if you have one) and its tiny but important
I downloaded the package file that I installed via https://fastly.cdn.openbsd.org/pub/OpenBSD/snapshots/packages/amd64/etsh-5.1.5v0.tgz .
It was the simplest approach for me, given that I installed it on my laptop that is running the syspatch(8) version of OpenBSD 6.3(-release).
So, I did
doas pkg_add -v etsh-5.1.5v0.tgz.
When I do a fresh install of OpenBSD 6.3-current (planning to wipe the hard drive), I should be able to do
doas pkg_add -v etsh, as is normal.
I’ll stop there.
You can get information about and install the binary package
You can also (build and) install it from the
shells/etsh directory of your local ports(7) tree, if you have one (and it’s up to date).
“There are many applications one might want to use on an OpenBSD system. To make this software easier to install and manage, it is ported to OpenBSD and packaged.” 
For a quick start, I would suggest you start by having a look at the ports(7) manual. If nothing else, jump to the end, make note of the commands in the SEE ALSO section. Please visit / read the following Web pages: OpenBSD Ports - Working with Ports and OpenBSD FAQ - Package Management.
Where you go now is up to you; if you have question(s), please do ask.
Thanks & Enjoy & Cheers! =^)