It also seems the diff listed is the wrong direction:
502d501 < if ($rcvd =~ /by web\S+\.mail\.mud\.yahoo\.com via HTTP/) { return
0; }

That line does not exist to be removed.
{^_^}
----- Original Message ----- 
From: "Matt Kettler" <mkettler_sa@[...].net> 
To: "Monty Ree" <chulmin2@[...].com> ; <users@[...].org>
Sent: 2005 June, 15, Wednesday 07:50
Subject: Re: FORGED_YAHOO_RCVD false positive


>  At 04:09 AM 6/15/2005, Monty Ree wrote:
>  >Hello, all.
>  >
>  >I have an account at yahoo.com and sent a mail to SA 3.0.x server at
>  >mail.yahoo.com site.
>  >But I have found that this legel mail was spam tagging and my header says
>  >that it was "FORGED_YAHOO_RCVD" violation.
>  >
>  >Anyone who uses mail.yahoo.com? please test this..
> 
> 
>  Yes, there are FP cases for this rule in SA 3.0.x. It's apparently been
>  fixed in the development versions of 3.1.0, but that's not yet released.
> 
>  http://bugzilla.spamassassin.org/show_bug.cgi?id=4264