WackoWiki converter resides at git repository.
Read the README before using converter - it is required to tweak couple of files.
If you want to transfer users as well, you can have a look at this. This repository contains two scripts: for dumping users from WackoWiki database and for pushing them to the MediaWiki database, and MediaWiki plugin necessary to authenticate users using password hashes from WackoWiki.
This plugin re-creates password hash on first login for each user, so once all users transferred from MediaWiki are logged in at least once, it is safe to remove this plugin from MediaWiki.