Descriptions can be found through The Open Content Page at http://www.opencontent.org/
The OpenContentLicense is at http://www.opencontent.org/opl.shtml
Open content documents are, like open source software, licensed by copyright holders to users to distribute and change.
An example is WikiPedia.
OpenDirectoryProject seems to be rolling along on a massive scale with an open content set-up, but not Wiki-related. Around 33,000 official volunteer editors are churning past 2.5 million human-reviewed web sites. I skimmed the license, seems simple, display a copyright notice with link back in their format, and you can have some or download it all. There's a line about the license being irrevocable, forever, even if the project shuts down. Just installed ODP++, Perl freeware - $50? $100? to remove the one, minimal Powered by... link back. Modular, templates to customize, with a local caching option, but doesn't even store data locally. Run the whole ODP through a fully customized interface, or filter down to whatever subsets you like. Pretty bizarre, especially with Netscape, Lycos, HotBot? all fellow ODP-users. -- MikeM
Also see BudapestOpenAccessInitiative, CreativeCommons, OpenArchivesInitiative, and PublicLibraryOfScience.