It seems to be as much of a unicorn as the source code itself. Can't find it on the official Lua page or google. Anyone who still has it?
The manual included with the 4.1 source code is the 4.0 version( the date matches Lua 4.0 release ). I saw someone mentioning a 4.1 version of it here: http://lua-users.org/lists/lua-l/2001-07/msg00187.html