The software used for this forum is an Open Source (Read: Free) set of PHP scripts which has become extremely popular on the internet recently. The scripts, together called "Phorum", are not only free but they provide more customization and features than some commercial alternatives.

Uboat.net indeed uses phorum, a wise choice for its needs, as do thousands of companies and organizations around the world who want a powerful, configurable forum solution which is free and easy to maintain.

Phorum has the added virtue of being written in PHP, which I have some familiarity with so that should the forum run into technical problems in the future, I may have some chance of finding its source.