Adding a wiki to a project
BOINC projects can, if they choose, add a wiki to the project website, using MediaWiki, the same software used by the Wikipedia.
Project administrators can easily control who is allowed to read or edit the wiki, based on special user status (eg. being an admin or moderator) or based on credit, recent or total. (Wikipedia chooses to allow editing by anybody as a matter of policy, not because it's built into the software). Thus it would be possible for project scientists to use the wiki to create documentation about the project, which the project volunteeers could read but not edit. Or it would be possible to allow some or all of the project volunteers to edit the wiki. It's up to the project to decide how to use the tool.
To add a wiki to your project you need simply to install MediaWiki (under the html directory is a good place, but the location doesn't matter) and then add to that the "BOINC Authentication" extension, which automatically logs people in to the wiki based on already being logged in to the BOINC project. There are two sample policy files available to show you how to easily adjust the automatic access controls.
The BOINC Authentication extension for MediaWiki is documented at http://www.mediawiki.org/wiki/Extension:BOINC_Authentication