The free version of the Security Ninja integration with MainWP can be downloaded and installed from the WordPress repository here:
https://wordpress.org/plugins/security-ninja-for-mainwp/
The free version is designed to read and display data exclusive to the free edition of Security Ninja. In compliance with the guidelines of the official WordPress repository, we are unable to include code in the repository that exclusively benefits Pro version users.
You can install the MainWP Addon via the WP Security Ninja Addon
The Pro extension works with websites running either Free or Pro version of Security Ninja – please check our installation instructions for the MainWP Addon.