While there may be a third party unix based system that could run in
the PowerPC processor hardware and give you some kind of choice
outside the better Mac OS X, depending on the processor speed, a
later OS X version may be installed. That is, If you can find it on DVD.
Or in the case of that obsolete PowerMac, with Jaguar 10.2. installed,
the hardware may be OK for hobby or other use. Mostly off-line.
There are no download upgrades, the official path would be retail Apple
system media on DVD, and depending on computer build model year &
specification, the upward limits in OS would be nowhere near the latest.
In fact the PowerPC hardware itself cannot support or run any OS X
after Leopard OS X 10.5.8; limits in processor speed, and other, were
addressed by significant changes with a move to Intel-based hardware.
If you wanted to run Snow Leopard OS X 10.6.8 (& gateway to later systems
that are online) you'd need at least a Intel Core2Duo CPU + 2- or 4GB RAM.
Your computer appears to be a PowerMac G4 tower, of a series that was
built over a period of perhaps four years, and saw update in build specs
within that period of time. To know for sure which one, you may have to
investigate details from the database of http://everymac.com and also
look into getting a download database from http://mactracker.ca to get
more information about the model build & different versions of PowerMac.
According to your old Mac specs, PowerMac G4 M5183 series' info here:
http://www.everymac.com/ultimate-mac-lookup/?search_keywords=M5183
Without more exact information, I'd venture to say something in the range
of Panther OS X 10.3.9 may be supported. Doubtful, but Tiger 10.4.11 is
a better system if the computer hardware could support & run it. An upgrade
to a later system usually invites or creates a need to also upgrade hardware.
Such as more RAM memory added, if the computer can use it, helps; plus
a larger capacity &/or faster spin rate hard disk drive with larger size cache
or buffer, can enhance data speed and other system function.
So to locate a later model Intel-based Apple Macintosh computer, portable or
desktop, would be a way to consider an OS X operating system of later era.
Hopefully this gives you some info to find vintage and obsolete products info.
Good luck & happy computing! 🙂
edited to add M5183 everymac link