seeking information on CiviCRM 4.1 version of "CRM/Core/BAO/PaymentProcessor.php" file
This was removed before CiviCRM moved to git, so I browsed the old Subversion repo.  I can see that revision 44887 removed it.  It's present if you click the first link but not the second:
http://svn.civicrm.org/civicrm/!svn/bc/44886/trunk/CRM/Core/BAO/
http://svn.civicrm.org/civicrm/!svn/bc/44887/trunk/CRM/Core/BAO/

I then attempted to view the SVN log, and then to check out the SVN repo:
svn log -v http://svn.civicrm.org/civicrm 
svn checkout http://svn.civicrm.org/civicrm/trunk civicrm

Both failed with a 503 error, I suspect this is to blame:
https://community.bitnami.com/t/varnish-throwing-503-on-svn-requests/25828

So I Googled "civicrm r44887" and found an IRC log:

[08:54] &lt;civi-bot&gt; r44887 by yashodha: CRM-11334 -- https://fisheye2.atlassian.com/changelog/CiviCRM?cs=44887


So there are your answers!  Check that atlassian.com link and CRM-11334, you'll find what you're looking for.