Is one of the preeminent forum software packages. The majority of forum packages are free to downlaod and use like phpbb, but they often require a linkback to their homepage from the footer of every page. vBulletin differs because it requires no linkback, but a one off license fee of $160.00 for each download, and $85.00 each for bulk orders. You will however only receive updates for one year, after this you will have to pay again for updates. Forum packages are often the target of hackers who scan the web for insecure installs. Therefore leaving a vBulletin installation alone without security updates is a risky venture. vBulletin does offer that little extra for the money however, it's generally considered the best forum package on the market, the most secure and perhaps the most search engine friendly as well.