Before being railroaded into Confluence, I argued vociferously for XWiki (https://www.xwiki.org/xwiki/bin/view/Main/ https://www.xwiki.org/xwiki/bin/view/Main/)

Before being railroaded into Confluence, I argued vociferously for XWiki (https://www.xwiki.org/xwiki/bin/view/Main/ https://www.xwiki.org/xwiki/bin/view/Main/). It's powerful, clean, and about as close to a Confluence replacement as you'll find anywhere. It can in fact import from Confluence. It has a number of useful extensions for it, though nowhere near as many as Confluence. Plus, it's open-source, and if you prefer the company behind the project also does convenient hosting. Of course, it doesn't integrate seamlessly with the other Atlassian products, but if you can do without that, it's definitely worth checking out.