ProcessWire is a free PHP open source CMS with a great API built to save you time and make development fun at any scale. Developed by Ryan Cramer Design, LLC
License: Open Source
Grav is a lightweight flat-file CMS that focuses on speed and simplicity, making it ideal for smaller projects and users comfortable with Markdown. ProcessWire, on the other hand, offers a more robust framework with extensive user management and content modeling capabilities, suited for larger and more complex websites.