Currently Being ModeratedJan 11, 2013 4:10 PM (in response to ENIGMACODE)
For 10.5, your friend is in luck--compatible ATI Radeon graphics drivers (including the PCIe X1900 G5 Series) are included as part of the Mac OS X 10.5 installation. You can verify this here:
The 10.5.8 update from Apple may have newer ATI drivers than the 10.5 DVD would have, of course.
Currently Being ModeratedJan 11, 2013 6:01 PM (in response to ENIGMACODE)
The X1900 G5 Edition has support from 10.4.7 with the ATI drivers update needed from 10.4.7 through 10.4.11.
As Brewster Magneto stated, OS X has the ATI X1xxx drivers native from 10.5 onward.