Anaconda itself was completely free, even for commercial use, until April 2020.
Since then, you need to buy a commercial license if you make commercial use of their repositories at https://repo.anaconda.com or the
anaconda channel on https://anaconda.org. The term commercial focuses on larger companies requiring more bandwith than a single OSS developer or scientist.
Read more about the details in the new Terms of Service or the Anaconda Commercial Edition FAQ.
The full EULA can be found here, and is also included in the installer (you must agree to it before installing Anaconda).
The gist of it is that you can use Anaconda however you want (including for commercial use). You only need to attribute it with something like “Powered by Anaconda”.
Note that the code itself for the packages in Anaconda may have other licenses, which may be more or less restrictive. For instance, most of the packages are BSD or similarly licensed, which is less restrictive. A few are GPL or LGPL, which are more restrictive. There is a list of the licenses of the Anaconda packages here.