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.
User contributions
From Reiser4 FS Wiki
This user is currently blocked. The latest block log entry is provided below for reference:
- 11:47, 19 February 2013 (diff | hist) . . (+218) . . FAQ ReiserFS (→What are the specs for ReiserFS: maximum number of files, of files a directory can have, of sub-dirs in a dir, of links to a file, maximum file size, maximum filesystem size, etc.?)