WordPress is free software that is written and maintained by thousands of volunteers around the globe. Not only is WordPress free, but it’s also open software — which means that the end user has the freedom to run, study, share/copy, and modify the software.
These “four freedoms” are codified into a software license called the GPL, or General Public License. The GPL is a copyleft license, which means that derived works can only be distributed under the same license terms. The license was originally written by Richard Stallman of the Free Software Foundation (FSF) for the GNU Project.
Freedom to run
Freedom to study
Freedom to copy and share
Freedom to modify
Because WordPress originated as a fork of the blogging software b2, which was licensed under the GPL, WordPress is also GPL software (and is required to carry the GPL). Other widely-successful examples of software licensed under the GPL include Linux kernel, the GNU Compiler Collection, and Drupal.
These are sources of background about WordPress and the GPL:
WordPress and the GPL
Themes are GPL, too
Why WordPress Themes are Derivative of WordPress
From the WordPress History on github:
Themes are GPL too
The Spirit of the GPL
WordPress core software is free, but other things you might need to use WordPress still cost money. Unless you want to buy a server, you’ll need to pay for website hosting. If you want your site to look a certain way, you can teach yourself how to design and develop websites, or you can buy a WordPress theme that looks the way you want your website to look. You can teach yourself how to use WordPress by reading documentation and experimenting, or you can pay someone to teach you. If you want WordPress to do something that the core software doesn’t currently do, you can teach yourself how to develop a plugin, or you can buy a plugin that provides that feature.
Now, there are lots of great WordPress themes and plugins on the wordpress.org repositories, and those have been reviewed for a certain base level of code quality and are also free. Lots of people run all their website(s) using the free themes and plugins from the WordPress repository, and do just fine. But some people prefer to use “premium” WordPress themes and plugins because of the additional support they might receive from the company or person selling that theme or plugin.
The WordPress community includes a booming economy of people earning their livings in WordPress-based businesses. People make money in the WordPress community in a few main ways:
1) Software as a service
4) Agency work
Let’s break them down one by one:
1) Using the software as a service (SaaS) model, theme and plugin companies sell a time- and/or site-limited subscription to automated software updates, bug fixes, and support. Access to these services can be sold on a per-site basis, but the use of the theme or plugin can not be restricted on a per-site basis because that would break the GPL.
When vetting a company that sells plugins or themes, look at their terms of service or licensing information, and also look at their pricing structure. If the pricing page indicates that the company restricts how many sites a theme or plugin can be used on, then that policy is breaks the GPL for that product.
2) Training: there are lots of free sources of information on how to use WordPress, including WordPress.tv and the Codex, but there are also lots of great teachers out there who charge money for WordPress training. This doesn’t affect the license at all, except we hope people also mention the license when training people to use WordPress. 🙂
3) Hosting: Anyone can get a free site on WordPress.com that uses WordPress, but if you want to do things with WordPress that WordPress.com does not allow or facilitate, then you’ll have to buy hosting and also possibly a domain name — unless you want to buy the equipment to set up your own servers and host your own site, but that’s going to cost more than buying even the more expensive hosting options.
4) Agency work: People who want to hire someone to build them a special WordPress website or feature for their personal or business website usually go to a web development agency. Agencies can be as small as one person or have thousands of employees. There are lots of web development agencies out there that specialize in WordPress, because they like how (comparatively) easy to use WordPress is for their clients, and they believe that open source software is high-quality software.
When vetting an organizer/speaker/company that is an agency or works for an agency, keep in mind that the GPL only applies to WordPress derivatives that are distributed works. If someone builds someone a WordPress theme or plugin for that person’s personal/business use, then the GPL does not require that the theme/plugin/derivative be publicly distributed. You don’t have to examine the licenses of all the custom themes someone has built in their agency work.