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Yes.

General requirements

Mac computer with an Intel, PowerPC G5, or PowerPC G4 (867MHz or faster) processor

512MB of memory
DVD drive for installation
9GB of available disk space
Some features require a compatible Internet service provider; fees may apply.
Some features require Apple's .Mac service; fees apply.
 
Confirmed. I installed Leopard this morning on a dual G4 mac pro with a DVD-R drive. It went through just fine, and it's good to see new life breathed into the ol' beast. 🙂

The Mac mini and Alum iMac just finished their upgrades without a hitch too. The MBP is undergoing it now.
 
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