While the free trial includes all features, the license key is intended to support the developer and remove the "Upgrade" prompts that appear periodically.
Prepros is a popular, user-friendly tool that allows you to compile, minify, and optimize your HTML, CSS, and JavaScript files with ease. Developed by Prepros, this software aims to simplify the development process by automating repetitive tasks, such as compiling Sass and Less files, minifying JavaScript and CSS files, and optimizing images. Prepros License Key
As of the last stable pricing model: