How to update an iMac G4 to run a Minecraft server?

Is it possible to update my iMac G4 to an OS and Java version that will be able to host a Minecraft server?

My internet speed, RAM, HD, and computer speed are not an issue, as it will be a small, private server.

Added (1). Lesus: OS X 10.2.8

What OS does it have now? Only early versions of Mac OS X can run on a G4.

According to the forum and other sources powerpc macs can only go up to java 5 and java 6+ is needed for recent minecraft versions
so no, you simply can't run minecraft on your powerpc mac.
http://forums.macrumors.com/showthread.php?t=1586753

p.s. It might be possible if you could run a ppc linux distro that works with java. You'd have to look into it though.