NetBSD is an operating system that runs on many platforms. NetHack is a computer game that runs on many platforms. (You can install NetHack above NetBSD by use of pkgsrc.) There are other similarities too.
- "Our contributors communicate primarily via email and Internet-based chat systems; many of us have never met each other in person. ... We believe that the Internet was an enabling technology that made NetBSD possible. The 'Net' in our name was thus chosen as a tribute to the Internet."
- "Why is it called NetHack if it's a single player game that doesn't use the net? The 'Net' in NetHack refers to the way the developers, many of whom have never met in person, organize the work on the program."
So the "Net" of both NetBSD and NetHack refers to that network, the Internet. This tribute may seem strange today, but that NetBSD and NetHack predate nearly all of today's projects. NetBSD 0.8 appeared at 20 April 1993, while NetHack 1.3d appeared on Usenet back in July 1987. The prefix "Net" also distinguishes these projects from the original BSD and Hack. The most important difference in organisation is that NetBSD has many developers and contributors, but NetHack has only its secretive DevTeam.
NetBSD comprises binaries for 53 "machine architectures" spanning 17 different types of processors. It might be interesting to see if NetHack, built through pkgsrc, can run on all of them. (You should instead be working toward ascension of all of the race-role-gender-alignment combinations.) If you lack hardware, you might try running NetBSD on emulated hardware. Note that the hardware list includes ancient hardware like the sun2 and embedded devices with limitted processing power like ARM evaluation boards. These are still powerful enough to run Unix-like systems, though.
NetHack has been on hardware that NetBSD could never support. An Intel 286, for example, is too weak for a Unix-like operating system, but can run old versions of NetHack with MS-DOS. NetBSD may be a very portable OS, but NetHack is a very portable game; NetHack is more portable than NetBSD.