Code inspected and checked and looks to be coded securely and implemented as expected. There is some additional complexity added by the vendor library which supports upgrading to the premium version of the plugin, however this is limited to the WordPress admin area, and also appears to be coded securely,
Reason for the 'Use with caution' result
The plugin has been given this recommendation at the tester's discretion:
Added as a use with caution because the additional complexity added by the freemius/wordpress-sdk library, which is only required to support upgrading to the paid for version.