Ok I just checked, and it does call main.inc.php just like I suspected...
###
### In pp-inc.php find this:
Find:
require "{$Globals['PP_PATH']}/languages/$pplang/pp-inc.php";
require "{$Globals['PP_PATH']}/languages/$pplang/login-inc.php";
Insert Below and set path to main-inc.php:
/// Require the library. Edit the path to the
// main.inc.php file if necessary.
require ("/PATH/TO/main.inc.php");
So from what I can tell, that compression code isn't even necessary and shouldn't be there.