Recycle iSight camera from G5
Yes. I have successfully and easily connected an iSight from a dead G5 iMac with iSight. I can confirm that the internal iSight is a USB connection despite the appearance of the connector (FireWire 1394). From the Apple Menu, choose about this Mac. Click get more information. Click USB and in the list you should see the iSight Camera as one of the ports.
To recycle / reuse your iSight camera, you will need an old USB cable that you cut. Clip off the (B-Male connector) which is the end away from the USB connector for your computer (A-Male connector). You should see a red, green, white and black cable. Strip the wires.
Unwrap the black metal tape from the camera cable near the connector and clip off the connector. You should see the same color coding, red, green, white, and black. Strip off those ends as well and connect the matching colors. I soldered the wires together and protected them with black electrical tape.
I suggest using a test computer to confirm your connections. Plug in the USB cable and you can use Quicktime to test out your camera.