A weighted GPA is one that is not measured on a 4.0 scale. For example, a PNM whose high school weighs honors and AP classes differently may choose to use a 5.0 or 6.0 scale.  Therefore, someone whose GPA is 2.75 on a 4.0 scale, may have a 3.43 on a weighted 5.0 scale. 
The problem as I see it, 
misplacedtexan, is that the only scale which really matters is the college scale, where a 4.0 is a 4.0 is a 4.0.  When I receive a transcript in a packet, I always provide the unweighted GPA on my rec because I know that my house is looking -- not at how did the student perform in her specific high school environment -- but how will she perform in college? 
I would look at the 
Bama Panhellenic FAQ regarding grades and the red/yellow/green zone.