Just to be clear about this point, since it seemed to spur a pretty detailed discussion: the joke I was making by bringing up TempleOS (and comparing it to a variant of the AmigaOS) solely involved the "OS as a religion" aspect of it, I by no means was trying to make fun of the author's condition. That article I linked to is actually a pretty interesting read in how it points out some parts of TempleOS are actually surprisingly clever and sophisticated; the man is certainly not stupid, he just... isn't quite on the right rails.I feel sorry for Terry. Obviously a brilliant mind if it weren't for the schizophrenia.
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Anyway. Back to the original topic... regarding the pros and cons of making "just another UNIX-like OS", the unavoidable fact is that an OS with no applications to run doesn't really do anyone any good. HelenOS goes out of its way to *not* be UNIX-like and the documentation (such as it is) is full of gotchays and limitations regarding its POSIX compatibility. This OS is itself being positioned as essentially a PowerPC-specific *fork* of HelenOS and therefore unlikely to attract more than... realistically, what, a few hundred users? so it's highly unlikely developers are going to spend a lot of time considering it as a build target, which means that any "mainstream" software anyone wants is going to have to be laboriously ported over along with any necessary foundational libraries. I guess none of that really matters if ultimately your goal is to make the "OS" a complete suit of minimal applications and not really a target for third party development, but... well, I guess we'll see if people are willing to pay $40,000 for that.
(My personal favorite "tiny" operating system that doesn't really try to be "standard" in any way is probably KolibriOS. Of course, being written entirely in assembly language makes it somewhat nontrivial to port.)
If the whole motivation really just revolves around not wanting to make "Another UNIX" at all costs I wonder if starting with, I dunno, the Haiku or Syllable codebases might be a better place to start. Both of those at least have a small suite of GUI desktop applications and foundation libraries already ported.
I dunno, maybe I'm overestimating how hard it'll be to port things to whatever HelenOS uses for a GUI. Good luck in any case.