FlatSiteBuilder is described as 'The FlatSiteBuilder is a very easy to use content management system and content creation tool running as a desktop application on Linux. You are able to build web content which you can host on github pages for free or any other web space provider' and is a CMS Tool in the Business & Commerce category. There are more than 100 alternatives to FlatSiteBuilder 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 FlatSiteBuilder are Drupal (Freemium, Open Source), Jekyll (Free, Open Source), Grav (Free, Open Source) and Joomla (Free, Open Source).
CSZ CMS is an open source web application that allows to manage all content and settings on the websites. CSZ CMS was built on the basis of Codeigniter and design the structure of Bootstrap, this should make your website fully responsive with ease.
Umbraco is a fully-featured open source content management system with the flexibility to run anything from small campaign or brochure sites right through to complex applications for Fortune 500's and some of the largest media sites in the world.
Noosfero is a web platform for social networks with blog, e-Porfolios, RSS, thematic discussion and events agenda in the same system. Get to know, use it, participate and contribute to this free software project.
Mezzanine is a powerful, consistent, and flexible content management platform. Built using the Django framework, Mezzanine provides a simple yet highly extensible architecture that encourages diving in and hacking on the code.