6
PSCounter never really took off because of several things, I couldn't be bothered to implement:
a) You will have to run the PHP-Stats on the same database as XOOPS
b) The "improved" Who's Online block is not 100% precise, yet
c) Other things, I cannot remember off the top of my head
If I recall correctly how to set it up is explained in the pscounter download, but I'm not sure.