If you see the Documents section you can spot a convo between the devs. http://lainos.sourceforge.net/MinddogConvo.php
Basically they intended to create a WM first as a base, then a file manager which works with the WM and then create the rest of the OS and the kernel.
In his own words:
"[00:23] [Neovanglist] LainOS is comprised of several projects, each to be completed in the following order
[00:23] [Neovanglist] LainWM - The Next Generation Window Manager
[00:24] [Neovanglist] LainFM - A standalone lightweight file manager which will also work in harmony with LainWM
[00:24] <minddog> interesting
[00:24] [Neovanglist] LainAM - A standalone program/driver/dependancy management system
[00:25] [Neovanglist] LainDM - a XDM/GDM type program to work with LainWM
[00:25] <minddog> hrmm so veering off of the /usr/ports idea?
[00:25] [Neovanglist] and then the LainOS kernel
[00:25] [Neovanglist] we are focusing on one project then moving on to the next
[00:25] [Neovanglist] with the ideal that it will make the code cleaner, and more interoperable
[00:25] [Neovanglist] since everyone who does LainFM (or most) will be moved from LainWM
[00:25] [Neovanglist] hence they will have an intimate knoledge of LainWM"
It's interesting to see the work that was put into this, and how, even in the early internet, there were dedicated communities and fandom's to Lain and other media.
I digged up the web archive and i found their old site and some more screenshots. https://web.archive.org/web/*/http://www.LainOS.org