The only problem with Confluence is that it's not open source. On the other hand, Atlassian does offer good deals, so if it's actually
free (or close to it) instead of literally open-source that you want, check it out.
I run the MediaWiki, which is the software that runs WikiPedia. I got it as a VM boot-and-go appliance. Open Source, easy install, and millions of people have found it usable.
On the other hand, for support, here's another consideration: The Trac system provides ticket management and tracking with online entry and reporting, tie-ins to source code repositories, AND a wiki. It's roughly equivalent to Atlassian's commercial issue management (Jira) plus wiki products.
This
thread needs to be moved, though. It's not really related to Jobs, so there should be a more appropriate forum for it.