msimplay,
phpbb is open source and FREE, hence the switch. IPB now costs $70 per year to keep it running, and the new trial versions are HIGHLY limited (maximum of 200 members, 1000 topics, etc.) Also, by using open source software, it can be modified however and as much as needed without violating any license agreements or breaking any copyright laws. It needs optimized to support more users online at once? We can do that. We can NOT do that with IPB anymore. Wanna rewrite the search function? We can do that with phpbb, but we can't do that with IPB anymore.