I'm not sure if this is much of a problem, but I noticed in the directory:
There's an .htaccess file with this in it:
# in case PHPIDS is placed in the web-root deny from all # silence is golden php_flag display_errors off
Some of the sites I host on, do not have mod_php as an Apache module. So the above reference of php_flag display_errors off would normally throw errors and possibly keep mute screamer from working correctly.
My suggestion for compatibility sake, is just to have the deny from all without the usage of the php_flag.