I'd recommend copying the copyrights page from sfwiki,daviswiki, scruzwiki, etc. In particular, it grants the ability to attribute to the project rather than a potentially long list of authors
Unless otherwise specified, content on this wiki is freely available to be copied, remixed, changed, augmented, and otherwise used by others without additional permission so long as they credit the author(s) such as through a link to the source. This is possible through a Creative Commons Attribution License (CC-BY).
Why Creative Commons Attribution (CC-BY)?
This license creates the right sort of freedom and flexiblity for others to reuse and remix OaklandWiki content, while respecting authors' contributions.
Why not Share-Alike?
Share-alike would prevent some derivative works when combining with resources that have other, incompatible licenses. Further, it would make value-add commercial difficult. Lastly, it would encourage incorporating other share-alike resources, which is not ideal, since new content with a very permissive license is much more valuable for the type of content on this wiki.
Why not CC0, the closest to a public domain license?
Can OaklandWiki content be used on Wikipedia?
Can Wikipedia content be used on Oaklandwiki?
Why not use dual licenses, with both cc-by and cc-by-sa?
Why not use different licenses for each page or each user?