Q: PowerMac G4 needs OSX upgrade

Sorry but that's impossible. A Power Mac G4 cannot run v10.11 El Capitan.

See requirements here >  OS X El Capitan - Technical Specifications

A Power Mac G4 can’t be upgraded past 10.5.8 and won’t ever have the Mac App Store(it requires at least 10.6.6.) If desired, buy a retail Mac OS X 10.5 package from a source such as Amazon or eBay.

(140844)

Not on a PowerPC Mac.

(140845)

crpender wrote:

 

So, to be clear, there is no bridge from OSX 10.5 to 10.6?

No.

There is no bridge. OS X 10.6 and later are for newer Macs that used Intel CPUs.

PowerMacs used a older IBM/Motorola CPU that is totally incompatible with OS X 10.6 and later.

Sorry.

The bridge is called get a new Mac with an Intel processor in it.