There is no age limit when using iChat. Anyone of any age is free to use it as they wish. Parents of younger children may want to ensure they know how their children are using iChat.
To communicate between a PC with a webcam and Macs using iChat you will need to get a free AIM name. You can then configure your AIM account to connect with iChat sessions. (See links below)
ichat
There is no Windows version of iChat yet but if the Windows user is using an AIM account then you can connect to the Mac iChat user if they are logged into iChat via an AIM account. Otherwise iChat will not work. You can also connect both users via a free online video/chat application similar to Skype, it's a very useful free video/chat application that cross's both Windows and Macs well.
iChat is provided free with all Mac computers (See links below) and can be installed from the Mac OS X installation discs. It is not legally available from any other source.
There is no version of iChat for Linux.
iChat uses the AIM network so to talk to people without iChat they will need to be on the AIM network. (See links below) .
ichat cost $29.00 to buy!!
Apple does not make iChat for iPad. But if you have an iPad 2 or newer, you can use FaceTime which is very similar to iChat.
"You cannot use ichat for Windows. Ichat is used with Mac, but you can use AIM with Windows and comunicate with Ichat on Mac. You will also need internet."
There is support for iChat on the Apple website, under the support option. They offer support for iChat when it quits unexpectedly, when the video chat is not working, and if you are unable to invite while in iChat.
In iChat, go to the top menu bar. Click "iChat" on the menu bar and then click "Change My Profile".