Well, define "run". The code can almost certainly compile to ARM object code, but whether that code could meaningfully interact with a router based on an ARM processor is an entirely different question, with no clear answer in the linked article.
I can't find anywhere they provide the source code. Maybe it's on the disk img, but in any event it's going to be pretty difficult to get it working on ARM without the creators getting involved.
Also it seems like I've heard routing performance in OpenBSD isn't that great on ARM. It typically also has trouble using hardware accelerators that are commonly used on ARM routers to get faster routing performance, which is why a lot of people build them with beefier x86 machines. I don't have a lot of experience with it OpenBSD on ARM though, so someone who knows better please correct me if I'm wrong.
The ARM SoC marketplace's common hardware denominator is the CPU. The rest of that system differs widely between vendors, and documentation for the pieces is poor-to-nonexistent.
Two OpenBSD devs run the Garbage.fm podcast [1], and they often lament about this state of ARM hardware.
ARM-based appliances (by Thecus, IO-DATA, and others) http://www.openbsd.org/armish.html
and not officially supported but being worked on
ARM-based devices, such as BeagleBone, BeagleBoard, PandaBoard ES, SABRE Lite, Nitrogen6x and Wandboard http://www.openbsd.org/armv7.html
one of the previous discussions: https://news.ycombinator.com/item?id=9482696