Well, no one really.
WordPress is a free and open-source content management system (CMS) based on PHP and MySQL. It was released on May 27, 2003, by its founders, Matt Mullenweg and Mike Little. Though largely developed by the developer community, WordPress is closely associated with Automattic, the company founded by Matt Mullenweg. On September 9, 2010, Automattic handed the WordPress trademark to the WordPress Foundation, which is an umbrella organization supporting WordPress.org (including the software and archives for plugins and themes). The point of the foundation is to ensure free access, in perpetuity, to the software projects it supports, including WordPress.
To best understand WordPress it is important that you first understand which WordPress you are talking about. The main cause for confusion is that often people don’t know that WordPress.com and WordPress.org are two fundamentally different products with different owners. Understanding the difference between the two is essential for understanding the ownership and business models behind the two products.
WordPress.org is often referred as self-hosted WordPress. The WordPress open source software package is made available at no cost through WordPress.org. It can be downloaded free to any third party server along with free plugins and themes. The key here is that you need to have your own registered domain as well a hosting solution for your WordPress site. And you need to stay on top of of all security updates to the framework, themes and plugins to keep your site secure. This option also gives the user access to custom themes and plugins through 3rd party developers.
WordPress.com on the other hand is a “free” web hosting service. It is owned by Automattic and is powered by the open source WordPress software. WordPress.com blogs are free for up to 3GB of storage space. Upgrades to storage space are available. Your blog domain is a sub domain (yourblog.wordpress.com) however a domain registration fee option is also available.
To better understand the difference between the .com & .org have a look at a comparison chart provided by wpbeginner.com.