...designed to build not so simple websites.
Diem is flexible. The developer creates its own modules by declaring them in simple configuration files. Then Diem generates a code which is 100% specific to the site's needs.
Diem packages many site-independant features in a clean user interface. Most of the common problems a web developer has to face up ( SEO, admin generation, search engine... ) are made easy.
Diem is, and will always be, entirely free and published under the MIT license.