The LSCache Module is built into your licensed copy of LiteSpeed Web Server. When it comes to caching dynamic content, the LSCache Module does all of the work.
The LSCache Plugin for WordPress is simply an interface. It allows WordPress to instruct the server Module on what to cache, how long to cache it, and when to purge. And it allows the site owner to manage and configure the Module. Without the Module, the Plugin could not function.
A licensed LSCache Module is required in order to use the free LSCache Plugin.