When you install Menu Image for the first time, you’ll be prompted to opt-in to Freemius or skip. Enabling it will help to improve Menu Image by securely sharing some data with Freemius.
What is Freemius?
Freemius is a framework that Menu Image to handle the code distribution, licenses, payments, subscriptions, refunds, etc.
The info collected will help us in case you need to submit a support ticket so we can see what is your WordPress version, PHP Version, Menu Image version and the language version. So no critical information is collected.
You can always skip it, and the plugin will still work just fine. There is no limitation in the plugin functionalities.
If you need read more about Freemius usage tracking.