I went googling for "Thoth operating system source code" while reading
the discussion on Unix-like OSes and found the following:
https://securitronlinux.com/debian-testing/nextstep-operating-system-source…
which led to
https://www.nextcomputers.org/forums/index.php?topic=4690.0
which led to various NeXTStep fragments that might be of interest.
Share and Enjoy!
Wesley Parish