I've been using phpBB3 for quite some time now. It seems to me this forum software hasn't evolved at all in all these years. Installing mods is a hassle, updating it to a newer version a real pain in the arse and moderating is not intuitive at all.

Besides, I find there's just no way to stop spam on it. Lots of web software have made a great job controlling spam, but phpBB3 still doesn't, at least not without too much complex and tedious work.

Since my last attempt to update to the latest version broke it, I'm finally fed up with it, and decide I'm not wasting a minute more in mantaining such a beast.

I'm looking for a free software (free as in free beer and free as in free speech) alternative. So SMF is not an alternative at the moment.

The most important feature I'm looking for is there must be a script to migrate all of the current phpBB users and posts into the new system.

Out of all the alternatives out there, does any of them support these features? Which one do you recommend?