This site is under construction and is both very incomplete and subject to change.
The current cannonical site for documentation is here.

Why would I share any data with Freemius?

When you share data with Freemius you basically share data with the product’s team. We are the data processor that acts on behalf of the plugin or theme developer. Think of Freemius as Google Analytics for WordPress plugins and themes, but instead of storing data about website traffic, the data is about the use of a plugin/theme.