Going back to this idea, the content of this forum would be licensed under the cc-wiki (http://creativecommons.org/licenses/by-sa/3.0/) license which is used by stackoverflow. A note to this effect would be added for example to all footers on the website, as well with a link to terms of use for the forum.
Existing content would remain as is, by default copyright of their respective authors. For the purposes of sharing the database publicly in the future, all posts past a certain date would be cc-wiki, and previous posts, as well as user private information, would be removed from the dumps.
If nobody minds, at some point in the future I'll pull requests towards this goal, tracked at https://github.com/nimrod-code/nimforum/issues/10.