Hi Robbie,
Short of time today but I'll hit the high spots:
Is "USB 2.0" another name for PowerMac6,4?
Yes. In addition to USB2 ports, the 6,4's have a faster bus (167 v 133 mhz) and will handle 2GB RAM.
Non-cataloged? I don't know what that means.
It means Apple never showed it in its regular retail line. It was made especially for the education market and sold only through Educational resellers and directly to schools. All it means was that Apple sold it to a school who eventually spun it off on the used market (assuming you got it used).
What is the best most updated OS that I could put on this eMac?
OS 10.5.8, If you call Apple an tell them you have a new iPad that needs 10.5, they may sell you a copy cheap. You need to use the 1-800-MY-APPLE number---it's not on the web store or in the retail outlets.
How good is this computer overall and compared to all other eMacs?
IMHO, it's the first of the "better" eMacs. The USB 1.1 eMacs struggle today. A fair number o the USB2.0s are still chugging along because they can run 10.5.8 better. The best is the last--the 1.42G. No history of problems and has a nicer video chipset that better supports the video technology in OS 10.5. Ours almost runs YouTube contents without the hacks (see next section)
I read that most or all video players, like Flash players, won't work anymore. I'm even having trouble with youtube. Is there a player that will work for video on Facebook that you know of, because Flashplayer doesn't update the version anymore?
Pretty much true as Adobe abandoned the PowerPC Mac not long after Apple did. I'm not the expert on that. Look in the PowerMac forum for posts by Texas Mac Man. He routinely posts links to some third-party workabouts that help with Flash content,
If I get the discs and redo everything, I'm thinking I could delete the languages after that. Is there any other useless stuff I can get rid of?
Printer support can go. Only install software for the printer you have.
What's keychain and airport, and do I need them?
Keychain is a built-in password manager that's been around since OS9. It is neither a RAM nor hard drive hog. Airport is Apple name for their wireless communication technology. They have a router called and Airport base Station and many Macs have a wireless card built in that is called, well, an "Airport card." Again, the software support for these is not a hog--I'd leave both alone. If your eMac has a wireless card installed, you need the Airport software. You can connect to any wireless router, not just the Apple ones, with that software if you have the card installed.
I have strong thoughts on the external drive issue. You can choose one that works well for this Mac plus will make the jump to a newer one if you upgrade. Will need to do that later today-sorry.
See ya!