Alternate Download Link: https://amazon.com/gp/drive/.../OS9General.dmg
This is a copy of Mac OS 9.2.2 for the PowerMac G4 MDD. The linked file is an OS X disk image named "OS9General.dmg" which was contained on the Software Restore CDs bundled with these systems. It includes "Applications (Mac OS 9)" and "System Folder". Unlike retail Mac OS 9 installers, this software is able to boot the PowerMac G4 MDD (FireWire 400 models) into OS 9 or can be used as Classic Mode on any PowerMac running Mac OS X v10.1-10.4. This System includes the Mac OS ROM file v9.6.1.
To use this software to boot an MDD in OS 9, use Disk Utility in Mac OS X (10.1-10.4) to format a hard drive in "Mac OS Extended" format, and be sure to choose the option to include Mac OS 9 Drivers. Once formatted mount the .dmg file and copy the System and Applications folders from the disk image to the hard drive. Restart your MDD via the Startup System Pref Pane or with the Option key held down, and select your Mac OS 9 drive as the Startup Disk.
For more info see my Vintage Mac Museum Blog: Reinstalling Mac OS 9 on a PowerMac G4 MDDCompatibility
Boots PowerMac G4 MDD (FireWire 400 models only); should also work for other Mac OS 9 compatible G3 or G4 Mac models. Usable as Classic Mode for all PowerPC Macs running Mac OS X.