In Mac OS X, Rosetta is the software that allows programs designed for PowerPC processors to work on Macs with Intel processors. You can "bring Rosetta back" by installing an older version of Mac OS X which supports it — Tiger, Leopard or Snow Leopard (on the latter it's. There was an emulation layer called Rosetta to allow Intel Macs to run PowerPC applications that Apple provided from Mac OS X to In Mac OS (El Capitan), some third-party applications may appear in the Applications folder with a prohibitory sign on top of their icons. I found an old Zoo Tycoon game and tried to download and play it on my MacBook Pro, but after it installed the app's picture was crossed out. Mac apps come in three different flavours: PowerPC, Universal and Intel. As you' d expect, the latter is fine, as all Macs these days run with Intel processors. Microprocessors belonging to the PowerPC architecture family have been used in numerous Apple used PowerPC processors in the Power Mac, iMac, eMac, PowerBook, iBook, Mac mini, and Xserve. Classic Macintosh accelerator boards . It is often easier to run old Windows applications than it is to run old Mac apps. I recall having a Windows version of this, check for that and. You're attempting to open a PowerPC application that isn't compatible with your version of the Mac operating system. You can no longer run powerPC apps or run MacOS 9 natively on modern Macs. Since Apple switched to Intel processors more than 10 years.