Depending on what you have, you might look at Xwiki (xwiki.com) or Bookstack (www.bookstackapp.com). I find Xwiki's look-and-feel not as nice as Confluence's, b

Depending on what you have, you might look at Xwiki (xwiki.com) or Bookstack (www.bookstackapp.com). I find Xwiki's look-and-feel not as nice as Confluence's, but they have many of the same features and they have a migration guide for importing data from Confluence.