I think you would
1. have to set up a server for that webcam stream on your mac...probably not fun.
2. find a free site that allows you to setup to stream your cam through them. Used to be several in the beginning of webcam, but may be harder to find now.
I understand you use adium to chat, but if it's a specific person on one of the services that allow webcam through their client, might be worth the two of you getting that client.
I use Skype, it's free pc to mac, mac to mac, pc to pc...so why not try that. If it's mac to mac, then ichat might be a good plan.
Also, there are things that use SIP connections, i'm not infront of my mac now, but i'll find out what it's called, and then someone on a pc could use the pc version.
anyway, there are options, just not particularly what you may be looking for.
Brian