“Contao Open Source CMS” is the full, official name of the project and says all you need to know when you first encounter the system. It is a CMS, i.e. a content management system under an open source license called Contao. If you already know what an open source CMS is, you can skip the next two sections. Otherwise …
A content management system is, by definition, a program for managing content. Within this very general category there are countless subgroups, such as
Contao is a Web Content Management System because it is designed to manage online content, unlike traditional content management systems that also serve radio and print media.
One characteristic of a content management system is that several users can work collaboratively on a project. Changes can be tracked at any time in version management and can be undone if necessary. In advance, an administrator can define in rights management which areas and contents users can access.
Furthermore, a CMS supports workflows. In Contao, you can allow an editor to create content but leave the publishing of that content to the editor-in-chief. This simple workflow guarantees that content doesn’t appear on the website until the editor-in-chief has reviewed it.
Even if you maintain a website all by yourself and don’t need any rights management or workflows, it still makes sense to use a CMS. A CMS makes your life much easier by breaking down tasks like creating and checking a form or embedding a Google Map - which means “you don’t have to know how it’s done technically”. To use Contao, you don’t need to know HTML, although it is the markup language used to create web pages.
Because Contao is installed on a web server, you have access to your data around the clock from anywhere in the world. So you can theoretically work on your website from a beautiful beach - although this could lead to problems during your family vacation.
Open source software is characterized above all by the fact that the comprehensive “free” use of the program is permitted and there is no restriction of licensees or areas of use. The openly accessible source code and freedom from license fees are essential prerequisites for free usability.
For you as a user, this means that you can use the program as you like - even for commercial projects. It is a common misconception that Open Source software may only be used for non-commercial projects. Such a “restriction of licensees” isn’t allowed in open source!
Of all Open Source licenses, the General Public License, or GPL for short, is probably the best known and most frequently used. It guarantees the licensee the right to use a program
In addition to these rights, the GPL also creates obligations for the licensee. For example, you may not remove any existing copyright notices or pass the program on under another license.
Further details and answers to common questions about Open Source licenses can be found on the website of ifrOSS, the Institute for Legal Issues of Free and Open Source Software.
Contao was initially licensed under the GPL, but is now licensed under the Lesser General Public License, short LGPL, which is a legal extension of the GPL. The main difference is that third party developers who write their own extensions for Contao are not required to put them under an Open Source license like they would under the GPL.