Most of the documentation is a snapshot of the old Namesys site (archive.org, 2007-09-29).
There was also a Reiser4 Wiki (archive.org, 2007-07-06) once on pub.namesys.com.
Reiser4 development appears to have stalled and ReiserFS is deprecated and scheduled to be removed from mainline Linux in 2025.
Talk:Future Vision
From Reiser4 FS Wiki
By Hans Reiser http://namesys.com 6114 La Salle ave., #405, Oakland, CA 94611 email: reiser@namesys.com