UPDATED 2012-09-07 This feature no longer works, it has been discontinued by Microsoft.
The Chat feature included in mojoPortal content management system is based on the Windows Live Messenger Web Toolkit. To use it you first need to get a Windows Live Application ID as documented here. Its not required to enable Windows Live Authentication in ordert o use the chat but it is recommended and can provide a better user experience.
There is a "Live Messenger Chat" feature that you can put on a page, as a supplement to the contact form for example and your web visitors will be able to chat with you no matter whether they have a Live Messenger account or not. You will chat using your desktop Live Messenger and the web control will display your availability and if you are online it will allow web visitors to initiate a chat with you. If the user does happen to have a Windows Live ID and is logged into your site using Windows Live, then when the user chats with you you can know his Windows Live screen name, otherwise the user will pick a name to use anonymously.
In addition to the new "Live Messenger Chat" feature that plugs into the content system, you can also enable your site users to have web chat controls on their profile page so that site users can initiate chat with one another. To receive chats a user will need the Live Messenger desktop software but chats can be initiated by web site visitors directly in the web page with no need for a Live account.
To enable chat on your mojoPortal user profile, visit the "My Account" page using the link at the top (after you sign in), click the profile tab, then click the link that says "Acquire/Refresh a Live Messenger Permission Token" (ok its mispelled in the screen shot but its fixed in the release)
You'll note that te checkbox is disabled until you have the token. Once you have the token the checkbox becomes enabled and if you check it ans save, the chat will appear on your public profile page like this: