"Security/2 is a multi-user system for OS/2. It provides controlled access
to files, drives, drivers and other OS/2 stuff, based on access control
list for each user.  Security/2 has modular structure and can be easily (i
hope ;)) extended and provides a API for developers to enable their
applications be multi-user." 

 Web site: http://os2.kiev.ua/en/sses.php
 Support forum: http://os2.kiev.ua/en/forum.list.php?f=5

 Download: ftp://ftp.os2.kiev.ua/sses/sses-alpha-0.2.5.zip

From Changelog:

0.2.5

  Added missing description of /no16bitcontrol switch to readme
  Added /alloweffective switch to sses.sys
  Added PUSERREGISTER3 structure to Security/2 API (see usertype.h)
  Added DosUserUnsetEffectiveUser to Security/2 API (see userctl.h)