UPDATE: 

The first check found this PHP errors during the installation attempt via Apps Market:

require_once([server_path]/modules/base/payment/classes/BxBaseModPaymentInstaller.php): failed to open stream: No such file or directory in <b>[server_path]inc/utils.inc.php

I found that EMP Community has "traded places" of the modules/base/payment and modules/boonex/payment folders. So when he changed this part back the error has passed away.