Hi:
I know it's not the same. I could not find any hits on GML and SAS.
However, it is possible to read an XML file with SAS -- so you might be able to read your GML file into a SAS dataset and then use that dataset with PROC GMAP. But PROC GMAP is meant to deal with a SAS dataset and with the maps contained in the SAS/Graph maps catalog.
So, even if you could read the XML file with SAS, that still leaves you with the issue of whether the GML coordinates correspond to the coordinates in the SAS/Graph map datasets used by PROC GMAP.
These papers may contain relevant information:
http://www2.sas.com/proceedings/forum2008/252-2008.pdf
http://www2.sas.com/proceedings/forum2008/253-2008.pdf
cynthia