XMB : XMB is a lightweight PHP forum software with all the features you need to support a growing community.
XMB

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Overview
XMB is a lightweight PHP forum software with all the features you need to support a growing community. With outstanding community support and contribution, you will find XMB to be easy to setup, customize, and enhance.

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Features

Though XMB is lightweight out of the box, it offers the key features you need to get your message board up and running