How do I network the iMac G5 to another Mac?

There are several ways to network the iMac G5 to another Mac.

Wirelessly (AirPort/AirPort Extreme)

Two AirPort Extreme (802.11g) equipped iMac G5 models or one AirPort Extreme equipped iMac G5 and another AirPort or AirPort Extreme-equipped Mac, can be networked together without the AirPort hardware access point by using "direct computer-to-computer communications" within a range of approximately 50 meters. AirPort Extreme was optional in the original models -- the iMac G5/1.6 17-Inch, G5/1.8 17-Inch, and G5/1.8 20-Inch -- and standard in subsequent "Ambient Light Sensor" and "iSight" models.

For Macs that have 10Base-T or 10/100Base-T or faster Ethernet installed and are capable of running MacOS 8.6 or higher, the first Mac can be added to an AirPort network via a crossover Ethernet cable between the computer and the hardware access point and the iMac can be added to the same network by the wireless AirPort Extreme connection if AirPort Extreme is installed.

Wired (Ethernet)

If you're not interested in using wireless networking, or your iMac G5 does not have AirPort Extreme installed, an iMac G5 also can be connected with a standard Ethernet cable to many other recent models. For older systems, assuming that Ethernet is installed, you can just use a simple crossover cable, or Ethernet cables and a hub, to connect another Mac to the iMac. Although it has not been updated in quite some time, Three Macs & A Printer covers basic types of wired networking in-depth.

Firewire

The iMac G5 can also be connected to another FireWire-equipped Mac, by using "FireWire Target Disk Mode". In this mode, the other computer simply will appear as a second hard drive on the desktop of the iMac. According to Apple "to use Target Disk Mode, simply connect the computers using a FireWire cable, then start the second computer while holding down the 'T' key on its keyboard."

For additional information, please refer to "How to Use Firewire Target Disk Mode".