Running Universal Binary Applications in Rosetta on Mac OS X
PowerPC software cannot run directly on Intel hardware.
To ease the hardware transition, Apple built a PowerPC emulator called Rosetta into the Intel version of Mac OS X "Tiger" (10.4.x) through "Snow Leopard" (10.6.x).
It was discontinued as of Mac OS X "Lion" (10.7.x).
Rosetta works transparently, meaning whenever you launch a PowerPC-native application, it will be automatically run through the Rosetta emulator.
Unfortunately, Intel-native applications cannot use Rosetta to load PowerPC-native plug-ins, drivers, or similar.
However, PowerPC-native applications, running through Rosetta, are able to load PowerPC-native plug-ins, drivers, etc.
Universal Binary applications, which typically include both PowerPC-native and Intel-native executables, can be set to "Open using Rosetta" -- meaning, they will run as PowerPC-native instead of the usually preferred Intel-native.
To enable this functionality, simply select the application and press Command-I, or select Get Info from the File menu.
The Get Info dialog includes a checkbox labeled "Open using Rosetta." Tick the box, and close the window.
From now on, whenever the application is launched, it will open in PowerPC mode, and PowerPC-native plug-ins, drivers, etc., will be available to it.
It is best to upgrade all components to Intel-native, because PowerPC-native applications running through Rosetta will run about 30% more slowly than Intel-native applications running on the same hardware.