<hr /><i>anonymous added on 2011-05-03 15:40:34 UTC:</i><br />
The issue likely comes from the use of 

  zPwdConv = mprintf("%/", zPwd);

in db_must_be_within_tree()->db_open_local().

This severely limits the usability of fossil for system configuration management. The mentioned workaround (mount -orebind) is only useful for Linux (FreeBSD's unionfs & nullfs do not allow such trickery with the root filesystem).