Gatsby is described as 'provides development teams an open source frontend framework for creating dynamic, optimized websites and a cloud platform for delivering them on a blazing fast edge network'. There are more than 50 alternatives to Gatsby for a variety of platforms, including Self-Hosted solutions, Online / Web-based, Windows, Linux and Mac. The best alternative is WordPress, which is both free and Open Source. Other great apps like Gatsby are Ghost (Paid, Open Source), Grav (Free, Open Source), Jekyll (Free, Open Source) and React (Free, Open Source).
It's lightning fast, developed from the ground up in C++, and released for free under the MIT license, use it for any of your personal or commercial projects – just be sure to preserve copyright and license notices!
Static Site Boilerplate is a free, open-source tool for developers that enables a better workflow for building modern static websites. Automated build processes, a local development server, production minification and optimizations, and the latest standards for static websites.