With Info.plist open in your favorite text editor, locate these strings:
<key>MinimumSystemVersion</key>
<string>10.5.3</string>
Edit the strings as follows:
<key>MinimumSystemVersion</key>
<string>10.4.11</string>
Save the changes and quit the editor. The demo works great on a first generation 3GHz Mac Pro with an ATI X1900XT video card.
[robg adds: System requirements are typically based on features in a given level of the OS, so there may be unknown issues if you use this hint to run the demo on an earlier version of the OS.] May be this will work for the full version too...

