My neighbor has a G5 iMac 17" (M9363LL/A) currently running OS X 10.3.9. They are experiencing issues with browsing the net, which I am assuming is due to the old version of Safari (1.3.2) and I have not been able to install a version of iTunes that is compatible with their iPod.

I attempted to install Firefox, but there is no version available anymore for 10.3, but I was able to locate a version of Opera which seems to have fixed the browsing issues temporarily.

I believe their G5 can be upgraded to Tiger or Leopard, but the issue is locating a legitimate copy.

I have seen some for sale on TradeMe, but there are a few things I am unclear on...

If I purchase discs that happen to be OEM from someone elses iMac, will they work on this machine?
I've noticed people asking questions as to if the discs are Black or Grey? Is there a difference in versions?
There are retail copies of Leopard for sale but they are near on $200!! Seems expensive seeing as I upgraded to Snow Leopard for $59!!
Do Apple hold copied of Tiger/Leopard for those customers who still have G5 machines and are wanting to upgrade?

Any suggestions or help will be greatly appreciated as I've only been a Macboy since intel...