It seems;

index.php - templates/wistie/Pligg.tpl - emplates/wistie/index_center.tpl - libs/link_summary.php - link_summary.tpl

where link_summary.php is where the category is assigned, in the code at the end;

global $display_grouplinks;

if(!isset($link_summary_output))

{$link_summary_output = '';}

if ($new_search) {

foreach($new_search as $link_id) {

$link->id=$link_id;

$link->read();

if( $display_grouplinks ) $link->link_group_id = 0;

$link_summary_output .= $link->print_summary('summary', true);

}

} else {

if ($links) {

foreach($links as $link_id) {

$link->id=$link_id;

$link->read();

$link_summary_output .= $link->print_summary('summary', true);

}

}

}

if(isset($fetch_link_summary) && $fetch_link_summary == true){

$main_smarty->assign('link_summary_output', $link_summary_output);

} else {

echo $link_summary_output;

}

Full details on UTSOnline in the Document section