In eZCollaborationItemGroupLink the methods fetch() and fetchList have variable comparisons instead of assignments:

When $userID is not provided (or false is given) to the methods fetch() and fetchList() the current user's ID should be used. Currently, $userID would remain false because it is compared to eZUser::currentUserID(); instead that the latter is assigned to the former.

if ( $userID == false )
    $userID == eZUser::currentUserID();