I'm not entirely sure if this is the best place for it, but...

My friend has an iMac G3 that runs Os 10.1.2 though he says it doesn't run well. He has a 56k modem. Could he play vendetta?

If he updates the OS to the latest version of 10.1.x (which is free, just use the Apple Updater) and it's faster than say, 300MHz, it could run VO with the lowest settings ok. The game works fine on a 56k modem.

It is REALLY worth it to upgrade to 10.3.x if you want good performance on that machine; however (if it has >512MB RAM) you might just want to wait for 10.4 if money is short.
-:sigma.SB