As to why, Gary didn't say.. or even contribute again, so we could surmise it was a made-up name to make sure the company he worked for wasn't identified, but some of the replies to his mail went into more detail about why they did, you can find them here
replyOr gentoo. Gentoo was pretty good around then, great to hack around with.
replyfreebsd = utility: performance, gnu software compatibility, drivers, closest thing to useful as a desktop (still not very), but almost x86 only
replyopenbsd = security: internet exposed services
netbsd = portability: already ported / most easily portable to every cpu arch & platform including old and new obscure ones. If you want a big-endian os for whatever academic reason, it's netbsd on an old sun sparc or pi3. I had an HP Jornada that had a SH3 cpu and shipped with wince, the only alternative os on that was netbsd.