I don't have foundation or 6.5 installed, I have a 6.5 somewhere I can deal with, but foundation no idea :|
For the code source stuff there is 2 things in fact

:
- sIBL_GUI : It's the multi-os / 3d packages sIBL Loader program.
- Templates : they are what sIBL_GUI chew up and are loaded in the target 3d application.
The code source of sIBL_GUI is available as the software is open source but it's not with him that the XSI 6.0 and 6.5 must be dealt, because he is blind and software independant, it's the template used for XSI 7.0 that need to be modified and adapted for XSI 6.5 / 6.02.
There is a browsable archive here with all the XSI Templates versions:
http://kelsolaar.hdrlabs.com/?dir=./sIBL_Framework/XSI/Templates/Mental%20RayIf you have some friends that can update one of the versions for XSI 6.5/6.02 don't hesitate to ask him (It would be a real time gain for me) and I will include it in the archive, etc