Lanai CMS is an open source content management system (CMS) framework that is module-based and uses template engines for page caching. It has two versions, with version 1xx being fully open source while version 2xx is open source but requires a subscription for extra modules and blocks. Lanai CMS is released under the GNU/GPL license and does not require annual or per-processor fees. It includes features like 25 modules, 30 themes, and development tools to generate code.