I think it is a bit my own fault, for not explaining in a clear way, what the difference is between WordPress.com and WordPress.org .
WordPress.com is a specialized blog-hosting site, on which members can write their blogs, but which runs on professionally-maintained servers, by WordpRess.com .
But, the people behind this service have also made the PHP Scripts available for free, that run on the server, and that cause the HTML to be generated, which causes proper WordPress blogs to appear on the browser of the reader. People may download those, and may upload them to whatever Web-server they have access to, provided that that Web-hosting service, also supports the running of server-side scripts, by the Web-hosting service members. Some Web-hosting services put a lot of restrictions on what their members may publish, such as static HTML Pages only, or such as no access to any MySQL server, the latter of which WordPress.org uses actually to store the blogs.
And so, because this support-factor is the main part of the expenses incurred by WordPress.com, I will assume that sharing their core scripts poses no perceived threat to them. Their main expense is not, that core set of PHP Scripts. But, because an individual may have problems setting all this up as well, there is an associated Web-site, namely WordPress.org, where independently-hosted WordPress users can go for tech support, and to download plug-ins.