If you searching in Google using keyword LAN Messenger for CMS,  Instant Messenger for Blog, Instant Messenger for Forum, Instant Messenger VBulletin, Instant Messenger Application PHP Source or IM for MySQL, you may find in the top of the result page, the LAN Messenger that should use not free. In this article,  I will give you one of Freeware (Even Open Source), LAN Instant Messenger Application called IntraMessenger.
You can use this LAN Messenger / Intra Messenger in a lot of website platform or Local Area Network. Such as:
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