The best open source alternative to WordPress is Drupal, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 100 alternatives to WordPress and loads of them is open source so hopefully you can find a suitable replacement. Other interesting open source alternatives to WordPress are Joomla (Free, Open Source), Ghost (Paid, Open Source), Grav (Free, Open Source) and Jekyll (Free, Open Source).
Omeka is a free, flexible, and open source web-publishing platform for the display of library, museum, archives, and scholarly collections and exhibitions. Its five-minute setup makes launching an online archive or exhibition as easy as launching a blog.
GeniXCMS is a PHP Based Content Management System and Framework (CMSF). It's a simple and lightweight of CMSF. Very suitable for Intermediate PHP developer to Advanced Developer. Some manual configurations are needed to make this application to work.
XOOPS CMS is an extensible, OO (Object Oriented), easy to use dynamic web content management system (CMS) written in PHP. XOOPS is the ideal tool for developing small to large dynamic community websites, intra company portals, corporate portals, weblogs and much more.
DNN provides a suite of solutions for creating rich, rewarding online experiences for customers, partners and employees. In addition to our commercial CMS and social community solutions, DNN is the steward of the DotNetNuke Open Source Project.